Fix builderName returned by acceptance.ProvisionImages().
Fix builderName returned by acceptance.ProvisionImages().

PiperOrigin-RevId: 487332239
Change-Id: I2092e2600080ead97fd8a2e91855e1db50359dee

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