Make fileMatch more specific

Hopefully, this makes it run faster and prevents potential false-positives.

Although.. a false-positive is unlikely anyway.

.github/renovate.json

@@ -5,7 +5,7 @@
 	],
 	"regexManagers": [
 		{
-			"fileMatch": [".*y[a]?ml$"],
+			"fileMatch": ["defaults/main.yml$"],
 			"matchStrings": [
 				"# renovate: datasource=(?<datasource>[a-z-.]+?) depName=(?<depName>[^\\s]+?)(?: (?:lookupName|packageName)=(?<packageName>[^\\s]+?))?(?: versioning=(?<versioning>[a-z-0-9]+?))?\\s+[A-Za-z0-9_]+?(?:_version|_tag)\\s*:\\s*[\"']?(?<currentValue>.+?)[\"']?\\s"
 			]