fix: invalid UTF-8 characters in commit message

[Ash-exp]

Description

For gRPC clients fetch git commits for pipelineId is breaking incase the commit message contains invalid UTF-8 characters.

Fixes devtron-labs/devtron#3930

How Has This Been Tested?

• Existing Git Material
  • commits having invalid UTF-8 in commit message
  • valid commit messages
• Create New Git Material
  • commits having invalid UTF-8 in commit message
  • valid commit messages

Checklist:

• The title of the PR states what changed and the related issues number (used for the release note).
• Does this PR requires documentation updates?
• I've updated documentation as required by this PR.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have tested it for all user roles.
• I have added all the required unit/api test cases.

Does this PR introduce a user-facing change?