Add Skip Changelog label to Dependabot-sourced PRs

[evantorrie]

Fixes #1158

Apologies for the redundancy herein, but neither Dependabot nor Github Actions support YAML anchors. https://github.community/t/support-for-yaml-anchors/16128/2

[codecov]

Codecov Report

Merging #1161 into master will decrease coverage by 0.3%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           master   #1161     +/-   ##
========================================
- Coverage    78.0%   77.7%   -0.4%     
========================================
  Files         135     135             
  Lines        7124    7153     +29     
========================================
- Hits         5559    5558      -1     
- Misses       1321    1352     +31     
+ Partials      244     243      -1     

Impacted Files	Coverage Δ
label/type_string.go	12.5% <0.0%> (-37.5%)	⬇️
sdk/export/metric/exportkind_string.go	64.2% <0.0%> (-35.8%)	⬇️
api/metric/kind_string.go	16.6% <0.0%> (-33.4%)	⬇️
api/metric/numberkind_string.go	25.0% <0.0%> (-25.0%)	⬇️
sdk/trace/batch_span_processor.go	78.5% <0.0%> (-1.1%)	⬇️