Remove SkylarkAttributeAspect and friends

This was added for some serialization code that no longer exists. It's never set in any
query results, so delete to avoid giving the impression it's useful.

AFAICT this isn't used anywhere, however if you find it is and this change breaks you,
you're best off just deleting your usage, since it was probably never doing what you
thought it was.

PiperOrigin-RevId: 253078501
diff --git a/src/main/protobuf/build.proto b/src/main/protobuf/build.proto
index 6c67d34..8f8374f 100644
--- a/src/main/protobuf/build.proto
+++ b/src/main/protobuf/build.proto
@@ -280,6 +280,8 @@
 
 // A rule instance (e.g., cc_library foo, java_binary bar).
 message Rule {
+  reserved 11;
+
   // The name of the rule (formatted as an absolute label, e.g. //foo/bar:baz).
   required string name = 1;
 
@@ -320,28 +322,11 @@
   // If this rule is of a skylark-defined RuleClass.
   optional bool is_skylark = 10;
 
-  // List of Skylark aspects that this rule applies.
-  repeated AttributeAspect skylark_attribute_aspects = 11;
-
   // Hash encapsulating the behavior of this Skylark rule. Any change to this
   // rule's definition that could change its behavior will be reflected here.
   optional string skylark_environment_hash_code = 12;
 }
 
-// A pairing of attribute name and a Skylark aspect that is applied to that
-// attribute.
-message AttributeAspect {
-  required string attribute_name = 1;
-  required SkylarkAspect aspect = 2;
-}
-
-// Aspect defined in Skylark.
-message SkylarkAspect {
-  required string extension_file_label = 1;
-  required string exported_name = 2;
-  repeated Attribute attribute = 3;
-}
-
 // Summary of all transitive dependencies of 'rule,' where each dependent
 // rule is included only once in the 'dependency' field.  Gives complete
 // information to analyze the single build target labeled rule.name,