[skip-changelog] Update golang to 1.21.1

[alessio-perugini]

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• Tests for the changes have been added (for bug fixes / features)
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• configuration.schema.json updated if new parameters are added.

What kind of change does this PR introduce?

What is the current behavior?

What is the new behavior?

Does this PR introduce a breaking change, and is titled accordingly?

Other information

[codecov]

Codecov Report

Patch coverage: 93.33% and project coverage change: -0.02% ⚠️

Comparison is base (4c0d72e) 63.06% compared to head (da4697e) 63.04%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2319      +/-   ##
==========================================
- Coverage   63.06%   63.04%   -0.02%     
==========================================
  Files         200      200              
  Lines       19206    19206              
==========================================
- Hits        12112    12109       -3     
- Misses       6049     6051       +2     
- Partials     1045     1046       +1     

Flag	Coverage Δ
unit	63.04% <93.33%> (-0.02%)	⬇️

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Files Changed	Coverage Δ
arduino/builder/detector/detector.go	74.34% <ø> (ø)
arduino/builder/export_cmake.go	7.98% <ø> (ø)
arduino/builder/libraries.go	81.25% <ø> (ø)
...er/preprocessor/internal/ctags/ctags_has_issues.go	98.58% <ø> (ø)
internal/cli/arguments/post_install.go	54.54% <ø> (ø)
internal/cli/completion/completion.go	91.66% <ø> (ø)
internal/cli/lib/search.go	54.91% <0.00%> (ø)
internal/inventory/inventory.go	53.19% <ø> (ø)
arduino/builder/cpp/cpp.go	93.22% <100.00%> (ø)
arduino/builder/preprocessor/ctags.go	68.62% <100.00%> (ø)
... and 4 more

... and 1 file with indirect coverage changes

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[umbynos]

LGTM