Coustard: fix copyright URL typo (bangers -> coustardFont)

Coustard: fix copyright URL typo (bangers -> coustardFont)

The copyright string for both the Regular and Black weights of the
Coustard family referenced https://github.com/googlefonts/bangers
in METADATA.pb, which is the URL of an unrelated font (Bangers).

The correct repository for Coustard is googlefonts/coustardFont,
which is the canonical fork modernized by Emma Marichal in
2026-03 (PR merged at upstream commit 84d4ef2fb) and matches the
repository_url already recorded in the source { } block.

The typo was introduced by Emma Marichal's gftools-packager run
in commit a0db74464 ("Coustard: Version 1.100; ttfautohint ... added",
2026-03-20), which onboarded the v1.100 update from the modernized
upstream. The packager populated the new copyright string by
template, but used the wrong repo URL.

Both fonts { } entries are updated:
- copyright: "Copyright 2011 The Coustard Project Authors
  (https://github.com/googlefonts/bangers)"
- ->
- copyright: "Copyright 2011 The Coustard Project Authors
  (https://github.com/googlefonts/coustardFont)"

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