Update dependency flat to v6

Author: renovate[bot]

package.json

@@ -101,7 +101,7 @@
     "js-yaml": "^4.1.1",
     "minimatch": "^3.0.5",
     "cookiejar": "^2.1.4",
-    "flat": "^5.0.1",
+    "flat": "^6.0.0",
     "qs": "6.15.2",
     "semver": "7.8.0",
     "@grpc/grpc-js": "1.14.4",

yarn.lock

@@ -3374,12 +3374,12 @@ __metadata:
   languageName: node
   linkType: hard
 
-"flat@npm:^5.0.1":
-  version: 5.0.2
-  resolution: "flat@npm:5.0.2"
+"flat@npm:^6.0.0":
+  version: 6.0.1
+  resolution: "flat@npm:6.0.1"
   bin:
     flat: cli.js
-  checksum: 10/72479e651c15eab53e25ce04c31bab18cfaac0556505cac19221dbbe85bbb9686bc76e4d397e89e5bf516ce667dcf818f8b07e585568edba55abc2bf1f698fb5
+  checksum: 10/c7a5f2e7e3ba0bec28b9c3aca27e68ff74df446df15cdb77ddef9e3d4fd0e9321ca52e49ca8b861c46157215006666b0dad25457f231083fc7bd2f7fcb67d7eb
   languageName: node
   linkType: hard