Tools: update release date checker to check for release date vs. last commit of release (#16712)

Signed-off-by: Michael Payne <michael@sooper.org>

Mirrored from https://github.com/envoyproxy/envoy @ 14782eb6bfd997d34dedba1b3ae9004e73a4ce86

bazel/repository_locations.bzl

@@ -36,7 +36,7 @@ REPOSITORY_LOCATIONS_SPEC = dict(
         sha256 = "0d3ca4ed434958dda241fb129f77bd5ef0ce246250feed2d5a5470c6f29a77fa",
         strip_prefix = "buildtools-4.0.0",
         urls = ["https://github.com/bazelbuild/buildtools/archive/4.0.0.tar.gz"],
-        release_date = "2021-02-03",
+        release_date = "2021-02-04",
         use_category = ["api"],
     ),
     com_github_cncf_udpa = dict(
@@ -115,7 +115,7 @@ REPOSITORY_LOCATIONS_SPEC = dict(
         sha256 = "39cc1fb45039c7687354ca497aff8a55c71d0f1e484f6b81124ba9d821c36441",
         strip_prefix = "opentelemetry-proto-{version}",
         urls = ["https://github.com/open-telemetry/opentelemetry-proto/archive/v{version}.tar.gz"],
-        release_date = "2020-12-09",
+        release_date = "2021-01-27",
         use_category = ["api"],
     ),
 )