Remove the deprecated exec_tools attribute from genrule.

RELNOTES: The `genrule` attribute `exec_tools` is removed. It has been identical to the `tools` attribute since Bazel 6.0 and uses should be updated.
PiperOrigin-RevId: 551546902
Change-Id: Ia59bf5db9c1c2c0d8828273c82762f8455e5f2f4

src/main/java/com/google/devtools/build/lib/rules/genrule/GenRuleBase.java

@@ -289,7 +289,6 @@ public String toString() {
   protected CommandHelper.Builder commandHelperBuilder(RuleContext ruleContext) {
     return CommandHelper.builder(ruleContext)
         .addToolDependencies("tools")
-        .addToolDependencies("exec_tools")
         .addToolDependencies("toolchains");
   }
 

src/main/java/com/google/devtools/build/lib/rules/genrule/GenRuleBaseRule.java

@@ -85,21 +85,6 @@ public RuleClass build(
                 .cfg(ExecutionTransitionFactory.createFactory())
                 .allowedFileTypes(FileTypeSet.ANY_FILE))
 
-        /* <!-- #BLAZE_RULE(genrule).ATTRIBUTE(exec_tools) -->
-        <b>Deprecated. Use <a href="#genrule.tools"><code>tools</code></a> instead.</b>
-
-        <p>
-          There was a period of time when <code>exec_tools</code> and <code>tools</code> behaved
-          differently, but they are now equivalent and the Blaze team will be migrating all uses of
-          <code>exec_tools</code> to <code>tools</code>.
-        </p>
-        <!-- #END_BLAZE_RULE.ATTRIBUTE --> */
-        .add(
-            attr("exec_tools", LABEL_LIST)
-                .cfg(ExecutionTransitionFactory.createFactory())
-                .allowedFileTypes(FileTypeSet.ANY_FILE)
-                .dontCheckConstraints())
-
         /* <!-- #BLAZE_RULE(genrule).ATTRIBUTE(outs) -->
         A list of files generated by this rule.
         <p>