Improve issue text for migrations
Some users were confused since they haven't been using incompatible flags.
Part of
@@ -34,7 +34,7 @@ FAIL_IF_MIGRATION_REQUIRED = os.environ.get("USE_BAZELISK_MIGRATE", "").upper()
REPO_PATTERN = re.compile(r"https?://github.com/(?P<owner>[^/]+)/(?P<repo>[^/]+).git")
-ISSUE_TEMPLATE = """Incompatible flag {flag} will break {project} once Bazel {version} is released.
+ISSUE_TEMPLATE = """Incompatible flag {flag} will be enabled by default in Bazel {version}, thus breaking {project}.
Please see the following CI builds for more information:
