mark test executable.

experimental_ui_test not being executable, causes test failures on
ci.bazel.build

RELNOTES: None.
PiperOrigin-RevId: 163726712
diff --git a/src/test/shell/bazel/bazel_experimental_ui_test.sh b/src/test/shell/bazel/bazel_experimental_ui_test.sh
old mode 100644
new mode 100755