chore: Fix gcov lib coverage build failure on macOS

[pratikmankawde]

High Level Overview of Change

Coverage builds on MacOS were failing on linking. This PR fixes the linking option.

This CI run shows that the build succeeds. MacOS image doesn't have coverage tools to generate reports hence the CI job fails.
https://github.com/XRPLF/rippled/actions/runs/21911026127/job/63264800263?pr=6350

Context of Change

For coverage builds, we try to link against the gcov library (specific to the environment). But Apple doesn't have this library. So, we don't need to explicitly force this linking. CodeCoverage.cmake:472-473

I removed the gcov suffix from both lines. The --coverage flag already:
On GCC: Automatically links against libgcov.a
On Clang/Apple Clang: Automatically links against the LLVM profile runtime

Why It Now Works on All Three Compilers
The file already had correct detection logic (lines 177-193):

Apple Clang: Uses xcrun -f llvm-cov → sets GCOV_TOOL="llvm-cov gcov"
Regular Clang: Finds llvm-cov → sets GCOV_TOOL="llvm-cov gcov"
GCC: Finds gcov → sets GCOV_TOOL="gcov"
The GCOV_TOOL is then passed to gcovr at line 416, so the correct tool is used for processing coverage data.

The fix ensures the linker flags are correct for all three compiler types.

Fixes #6349.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Performance (increase or change in throughput and/or latency)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update
• Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• Release

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.9%. Comparing base (9f17d10) to head (0150c87).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #6350   +/-   ##
=======================================
  Coverage     79.9%   79.9%           
=======================================
  Files          840     840           
  Lines        65508   65508           
  Branches      7254    7252    -2     
=======================================
  Hits         52346   52346           
  Misses       13162   13162           

see 2 files with indirect coverage changes

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[mathbunnyru]

Great change and description 👍

And probably the longest branch name I've seen in a while 😂