Enable tests for go115.
Enable tests for go115.

PiperOrigin-RevId: 324629160
Change-Id: Iee078cd3bbf1038fdee860c44a890b3f4abcf114

GoogleCloudPlatform/buildpacks,GoogleCloudPlatform/buildpacks,GoogleCloudPlatform/buildpacks,GoogleCloudPlatform/buildpacks