[renovate] Fix match for all base branches (#205963)

https://docs.renovatebot.com/string-pattern-matching/ doesn't appear to
be working for this setting.

The documentation [mentions regular expression
support](https://docs.renovatebot.com/configuration-options/#matchbasebranches),
this moves the expression over.

renovate.json

@@ -67,7 +67,7 @@
         "team:kibana-operations"
       ],
       "matchBaseBranches": [
-        "*"
+        "/^[8-9].*/"
       ],
       "labels": [
         "Team:Operations",
@@ -94,7 +94,7 @@
         "team:kibana-operations"
       ],
       "matchBaseBranches": [
-        "*"
+        "/.*/"
       ],
       "labels": [
         "Team:Operations",
@@ -3213,7 +3213,7 @@
         "team:kibana-operations"
       ],
       "matchBaseBranches": [
-        "*"
+        "/.*/"
       ],
       "labels": [
         "Team:Operations",