Update prometheus labels

[aledbf]

Which issue this PR fixes : fixes #2787

[antoineco]

/lgtm
sed for the win

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf, antoineco

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[codecov-io]

Codecov Report

Merging #2790 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2790      +/-   ##
==========================================
+ Coverage   47.57%   47.58%   +0.01%     
==========================================
  Files          75       75              
  Lines        5413     5413              
==========================================
+ Hits         2575     2576       +1     
+ Misses       2511     2509       -2     
- Partials      327      328       +1

Impacted Files	Coverage Δ
internal/ingress/metric/collectors/socket.go	79.72% <100%> (ø)	⬆️
internal/watch/file_watcher.go	84.61% <0%> (+3.84%)	⬆️

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