apache-beam[gcp] dependency issue with dataflow/flex-templates/getting_started/requirements.txt

## In which file did you encounter the issue?
dataflow/flex-templates/getting_started/requirements.txt

## Did you change the file? If so, how?
`apache-beam[gcp]==2.48.0` to `apache-beam[gcp]==2.*` and added `google-auth-httplib2==0.2.*`

## Describe the issue
While building the example as stated in [the getting started documentation here](https://cloud.google.com/dataflow/docs/guides/templates/using-flex-templates#build-template), you will get an error stating:
`ERROR: Cannot install apache-beam[gcp]==2.48.0 and google-auth-httplib2==0.2.0 because these package versions have conflicting dependencies.` this is because I think the current version of `apache-beam[gcp]` is `2.60.0` and conflicts with other dependencies as `2.48.0` uses an older `google-auth-httplib2` dependency.

My suggestion is to just include the major versioning `2.*` as for the example it might not be that important to have a fully fixed version.