Remove aspect toolchain transition API.

Part of #15346.

PiperOrigin-RevId: 446516247
diff --git a/src/main/java/com/google/devtools/build/lib/packages/AspectDefinition.java b/src/main/java/com/google/devtools/build/lib/packages/AspectDefinition.java
index d568f30..ddf2d87 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/AspectDefinition.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/AspectDefinition.java
@@ -67,7 +67,6 @@
   private final RequiredProviders requiredProvidersForAspects;
   private final ImmutableMap<String, Attribute> attributes;
   private final ImmutableSet<ToolchainTypeRequirement> toolchainTypes;
-  private final boolean useToolchainTransition;
 
   /**
    * Which attributes aspect should propagate along:
@@ -103,7 +102,6 @@
       RequiredProviders requiredProvidersForAspects,
       ImmutableMap<String, Attribute> attributes,
       ImmutableSet<ToolchainTypeRequirement> toolchainTypes,
-      boolean useToolchainTransition,
       @Nullable ImmutableSet<String> restrictToAttributes,
       @Nullable ConfigurationFragmentPolicy configurationFragmentPolicy,
       boolean applyToFiles,
@@ -116,7 +114,6 @@
     this.requiredProvidersForAspects = requiredProvidersForAspects;
     this.attributes = attributes;
     this.toolchainTypes = toolchainTypes;
-    this.useToolchainTransition = useToolchainTransition;
     this.restrictToAttributes = restrictToAttributes;
     this.configurationFragmentPolicy = configurationFragmentPolicy;
     this.applyToFiles = applyToFiles;
@@ -143,10 +140,6 @@
     return toolchainTypes;
   }
 
-  public boolean useToolchainTransition() {
-    return useToolchainTransition;
-  }
-
   /**
    * Returns {@link RequiredProviders} that a configured target must have so that this aspect can be
    * applied to it.
@@ -280,7 +273,6 @@
     private boolean applyToFiles = false;
     private boolean applyToGeneratingRules = false;
     private final Set<ToolchainTypeRequirement> toolchainTypes = new HashSet<>();
-    private boolean useToolchainTransition = false;
     private ImmutableSet<AspectClass> requiredAspectClasses = ImmutableSet.of();
 
     public Builder(AspectClass aspectClass) {
@@ -595,11 +587,6 @@
       return this;
     }
 
-    public Builder useToolchainTransition(boolean useToolchainTransition) {
-      this.useToolchainTransition = useToolchainTransition;
-      return this;
-    }
-
     /**
      * Builds the aspect definition.
      *
@@ -620,7 +607,6 @@
           requiredAspectProviders.build(),
           ImmutableMap.copyOf(attributes),
           ImmutableSet.copyOf(toolchainTypes),
-          useToolchainTransition,
           propagateAlongAttributes == null ? null : ImmutableSet.copyOf(propagateAlongAttributes),
           configurationFragmentPolicy.build(),
           applyToFiles,
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/proto/CcProtoAspect.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/proto/CcProtoAspect.java
index d1608e0..c30d309 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/proto/CcProtoAspect.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/proto/CcProtoAspect.java
@@ -127,7 +127,6 @@
                     // can be optional.
                     .mandatory(true)
                     .build())
-            .useToolchainTransition(true)
             .add(
                 attr(PROTO_TOOLCHAIN_ATTR, LABEL)
                     .mandatoryProviders(ProtoLangToolchainProvider.PROVIDER_ID)
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/J2ObjcAspect.java b/src/main/java/com/google/devtools/build/lib/rules/objc/J2ObjcAspect.java
index 4a5caa9..4cc296a 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/J2ObjcAspect.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/J2ObjcAspect.java
@@ -155,7 +155,6 @@
                 // be optional.
                 .mandatory(true)
                 .build())
-        .useToolchainTransition(true)
         .add(
             attr("$grep_includes", LABEL)
                 .cfg(ExecutionTransitionFactory.create())