fix(ci): don't run all tests on exclusions change (GoogleCloudPlatform#3983)

ignore ".github/config/" so changes to the configs aren't
considered global changes (which cause all packages to
be tested)

Author: briandorsey

.github/config/nodejs-dev.jsonc

@@ -24,6 +24,7 @@
     "secrets": { }
   },
   "ignore": [
+    ".github/config/", // prevent changes to exclusions from running all tests
     ".eslintignore",
     ".eslintrc.json",
     ".github/.OwlBot.lock.yaml",

.github/config/nodejs-prod.jsonc

@@ -24,6 +24,7 @@
     "secrets": { }
   },
   "ignore": [
+    ".github/config/", // prevent changes to exclusions from running all tests
     ".eslintignore",
     ".eslintrc.json",
     ".github/.OwlBot.lock.yaml",