[NO-TICKET] Specify Python version for snyk

[joneill-r7]

Specify the python version for snyk to run on the correct python version.

Created .snyk file as mentioned on this doc to use version 1.25.0

And then matched the major.minor python version we want to scan for this repo - as we can't specify the patch version. Python docs in snyk link

Running on this version (3.9.18) passes whereas snyk is showing differently.
Snyk: snyk results
Local:

(venv) joneill:mimecast/ (snyk-bump-python✗) $ python --version                                                            [14:48:57]
Python 3.9.18
(venv) joneill:mimecast/ (snyk-bump-python✗) $ snyk test                                                                   [14:49:01]

Testing /Users/joneill/insightconnect-plugins/plugins/mimecast...

Organization:      soar-insightconnect-new
Package manager:   pip
Target file:       requirements.txt
Project name:      mimecast
Open source:       no
Project path:      /Users/joneill/insightconnect-plugins/plugins/mimecast
Licenses:          enabled

✔ Tested 11 dependencies for known issues, no vulnerable paths found.

Next steps:
- Run `snyk monitor` to be notified about new related vulnerabilities.
- Run `snyk test` as part of your CI/test.