[infra] Remove trailing new-line from auth token file
[infra] Remove trailing new-line from auth token file

The result from 'gcloud auth print-access-token' contains a
new-line that cannot be used in the header. To make this use case
easier, remove new-lines, if found.

Change-Id: I44a9cc2bcfe4a8ef06e47a8495e69e116e9a6dfa
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/153921
Commit-Queue: Karl Klose <49bc0b76cffb0b10cd8c84f9cabc97a31ffe6343@google.com>
Reviewed-by: William Hesse <a821cddceae7dc400f272e3cb1a72f400f9fed6d@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk