Reduce `air` verbosity (#31417) (#31425)

Backport #31417 by @silverwind

Make `air` log less. Uses the option added in
https://github.com/air-verse/air/pull/367.

Co-authored-by: silverwind <me@silverwind.io>

.air.toml

@@ -21,3 +21,6 @@ exclude_dir = [
 ]
 exclude_regex = ["_test.go$", "_gen.go$"]
 stop_on_error = true
+
+[log]
+main_only = true