Removes "-preview" hack for Android build tools version attribute.

This has been a no-op since commit 9a21e20.

--
MOS_MIGRATED_REVID=127771957

src/tools/android/java/com/google/devtools/build/android/Converters.java

@@ -135,12 +135,6 @@ public static class FullRevisionConverter implements Converter<FullRevision> {
     @Override
     public FullRevision convert(String input) throws OptionsParsingException {
       try {
-        // TODO(bazel-team): The current version of FullRevision doesn't know
-        // how to properly parse build tool revisions with "-preview", and
-        // upgrading to the lastest version will take time. Since we don't
-        // currently need to distinguish between preview and non-preview build
-        // tools, for now just remove the suffix.
-        input = input.replace("-preview", "");
         return FullRevision.parseRevision(input);
       } catch (NumberFormatException e) {
         throw new OptionsParsingException(e.getMessage());