Use labels source for alerts/template

[github-actions[bot]]

Benchmark diff:

goos: linux
goarch: amd64
pkg: github.com/cloudflare/pint/cmd/pint
cpu: AMD EPYC 7763 64-Core Processor                
              │   old.txt   │              new.txt               │
              │   sec/op    │   sec/op     vs base               │
FindEntries-4   39.61m ± 1%   39.92m ± 2%       ~ (p=0.280 n=10)
CheckRules-4     8.498 ± 2%    8.502 ± 2%       ~ (p=0.853 n=10)
geomean         580.2m        582.6m       +0.41%

              │   old.txt    │               new.txt               │
              │     B/op     │     B/op      vs base               │
FindEntries-4   27.41Mi ± 0%   27.41Mi ± 0%       ~ (p=0.853 n=10)
CheckRules-4    977.2Mi ± 0%   988.7Mi ± 0%  +1.18% (p=0.000 n=10)
geomean         163.7Mi        164.6Mi       +0.59%

              │   old.txt   │              new.txt               │
              │  allocs/op  │  allocs/op   vs base               │
FindEntries-4   131.9k ± 0%   131.9k ± 0%       ~ (p=0.896 n=10)
CheckRules-4    14.19M ± 0%   14.30M ± 0%  +0.82% (p=0.000 n=10)
geomean         1.368M        1.373M       +0.41%

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.79%. Comparing base (012cb00) to head (0545edc).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1163 +/- ## ======================================= Coverage 94.79% 94.79% ======================================= Files 104 104 Lines 12274 12202 -72 ======================================= - Hits 11635 11567 -68 + Misses 487 485 -2 + Partials 152 150 -2 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.