Fixed TestAccComputeRegionNetworkEndpointGroup_regionNetworkEndpointGroupAppengineExample

[modular-magician]

Resolved hashicorp/terraform-provider-google#8937.

Switched off the default service to a new one.

This test relies on an app engine instance; the failure was in app engine initialization rather than in the configuration that was actually needing to be tested. I copied the configuration from a passing app engine test, and this now passes.

This pr also changes the line endings in the template file, so it might be useful to turn on whitespace ignoring to review.

Run of just this test: https://ci-oss.hashicorp.engineering/buildConfiguration/GoogleCloud_ProviderGoogleCloudMmUpstream/185685

This does end up taking about 2x as long as the test previously took (i.e. 8min instead of 4min); I'm definitely open to suggestions if you have any!

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Derived from GoogleCloudPlatform/magic-modules#4761