fix: make removal smoother and successful (#26)

Co-authored-by: Sally Young <git@justa.fish>

Author: rfay

install.yaml

@@ -30,7 +30,10 @@ post_install_actions:
   - cd ../core && ddev yarn
 
 removal_actions:
-  - rm core/phpunit.xml
-  - rm -rf test_output
-  - rm core/.env
-  - rm .gitignore
+  - |
+    for item in ../core/phpunit.xml ../core/.env ../.gitignore; do 
+      if grep '#ddev-generated' ${item} >/dev/null; then
+        rm -f ${item}
+      fi
+    done
+  - rm -rf ../test_output