Resolve "Snippet update error when version feature flag disabled"

What does this MR do?

As discussed in #213367 (closed), this MR modifies the internal git api for snippet repos when the version_snippets feature flag is disabled, so that it allows the check to continue if the protocol is "web" (i.e. the request is being made as a result of an action through the UI).

This is because otherwise user's will experience the The project you were looking for could not be found error if they attempt to update a versioned snippet, if the feature flag is disabled for them (or globally) later on.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation ([if required](https://docs.gitlab.com/ee/development/documentation/workflow.html#when-documentation-is-required))
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Closes #213367 (closed)