chore: patch bump lerna things and use 4.0.0 as default

.changeset/wicked-forks-sleep.md

@@ -1,5 +1,6 @@
 ---
 '@backstage/cli': patch
+'@backstage/create-app': patch
 ---
 
-Upgrading to lerna@4.0.0 in CLI
+Upgrading to lerna@4.0.0.

package.json

@@ -50,7 +50,7 @@
     "concurrently": "^5.2.0",
     "fs-extra": "^9.0.0",
     "husky": "^4.2.3",
-    "lerna": "^3.20.2",
+    "lerna": "^4.0.0",
     "lint-staged": "^10.1.0",
     "prettier": "^2.0.5",
     "recursive-readdir": "^2.2.2",