internal/civisibility: auto test retries max retries fix

[tonyredondo]

What does this PR do?

This PR fixes the calculation and message of auto test retries maximum number of retries for the session.

Motivation

The decrement was executed during every shouldRetry call even if a retry is not being done at the end.

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.

Unsure? Have a question? Request a review!