test: update base project for E2E tests to version 15

Update the base update E2E test project to the minimum supported Angular version.

(cherry picked from commit 442d7bc)

Author: alan-agius4

tests/legacy-cli/e2e/assets/14.0-project/.browserslistrc

@@ -1,6 +1,6 @@
-# FourteenProject
+# FifteenProject
 
-This project was generated with [Angular CLI](https://github.com/angular/angular-cli) version 14.2.5.
+This project was generated with [Angular CLI](https://github.com/angular/angular-cli) version 15.2.8.
 
 ## Development server