fix(secret): Asymmetric Private Key shouldn't start with space

[DmitriyLewen]

Description

There are times when Asymmetric Private Key example uses space.
e.g. https://github.com/googleapis/google-api-python-client/blob/a999ad0d152d6404d379c8332bc27abfe85ba7d7/googleapiclient/discovery_cache/documents/appengine.v1.json#L2088
To avoid these cases Asymmetric Private Key shouldn't start with space.

Related PRs

• fix(secret): remove spaces from asymmetric private key #2434
• fix: update the regex for secrets scanning #2964

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).