chore(renovate): migrate the configuration to plain JSON

The JSON5 syntax was not used for anything that JSON cannot express. The only comment-looking entry was already a
`description` field, which renovate evaluates itself and which therefore survives the conversion. Plain JSON is the
better default here, because it needs no dedicated parser in editors and tooling.

The converted configuration was verified against the JSON5 parser to be structurally identical to its predecessor.

Co-authored-by: Copilot <copilot@github.com>

.helmignore

@@ -36,6 +36,6 @@ unittests/
 .prettierignore
 .yamllint
 CODEOWNERS
-renovate.json5
+renovate.json
 .commitlintrc.json
 .gitsv/