chore: update flint to v0.21.0

Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>

Author: zeitlinger

.github/config/lychee.toml

@@ -12,6 +12,8 @@ include_fragments = true
 exclude = [
   # excluding links to pull requests and issues is done for performance
   "^https://github.com/open-telemetry/opentelemetry-java-contrib/(issues|pull)/\\d+$",
+  # developer.ibm.com intermittently returns 500 for MQ downloads
+  "^https://developer\\.ibm\\.com/articles/mq-downloads/$",
   # groovy-lang.org is frequently unreachable / times out
   "^https?://[^/]*groovy-lang\\.org",
 ]

mise.toml

@@ -6,7 +6,7 @@ actionlint = "1.7.12"
 biome = "2.4.13"
 editorconfig-checker = "3.6.1"
 "github:google/google-java-format" = "1.35.0"
-"github:grafana/flint" = "0.20.4"
+"github:grafana/flint" = "0.21.0"
 "github:jonwiggins/xmloxide" = "0.4.2"
 "github:koalaman/shellcheck" = "0.11.0"
 ktlint = "1.8.0"