Clean up a few Windows warnings

[mjcarroll]

🦟 Bug fix

Related to: gazebosim/gz-sim#1771

Summary

Remove some Windows warnings.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov]

Codecov Report

Merging #308 (02b0d83) into gz-fuel-tools8 (c1acd16) will increase coverage by 0.75%.
The diff coverage is n/a.

@@                Coverage Diff                 @@
##           gz-fuel-tools8     #308      +/-   ##
==================================================
+ Coverage           73.77%   74.52%   +0.75%     
==================================================
  Files                  20       20              
  Lines                2871     2866       -5     
==================================================
+ Hits                 2118     2136      +18     
+ Misses                753      730      -23     

Impacted Files	Coverage Δ
src/ClientConfig.cc	81.70% <ø> (-0.39%)	⬇️
src/FuelClient.cc	67.33% <ø> (ø)
src/Interface.cc	83.92% <ø> (-1.79%)	⬇️
src/gz.cc	48.88% <ø> (+7.44%)	⬆️
src/RestClient.cc	67.42% <0.00%> (-4.55%)	⬇️

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