Use Bazel Preconditions variant which avoids varargs array creation

Reduces garbage.

--
MOS_MIGRATED_REVID=109914243
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/ValidationEnvironment.java b/src/main/java/com/google/devtools/build/lib/syntax/ValidationEnvironment.java
index 03847ac..8c625d8 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/ValidationEnvironment.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/ValidationEnvironment.java
@@ -14,8 +14,8 @@
 
 package com.google.devtools.build.lib.syntax;
 
-import com.google.common.base.Preconditions;
 import com.google.devtools.build.lib.events.Location;
+import com.google.devtools.build.lib.util.Preconditions;
 
 import java.util.HashMap;
 import java.util.HashSet;