plugin/error: use warning instead of warn (#4738)

We use the 'WARNING' in the logs, instead of warn, so make the change
here as well for consistency sake.

Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/errors/setup_test.go

@@ -79,9 +79,9 @@ func TestProperLogCallbackIsSet(t *testing.T) {
 		wantLogLevel     string
 	}{
 		{
-			name: "warn is parsed properly",
+			name: "warning is parsed properly",
 			inputErrorsRules: `errors {
-		        consolidate 1m .* warn
+		        consolidate 1m .* warning
 		    }`,
 			wantLogLevel: "[WARNING]",
 		},