Build system: Don't delete .gitignore when creating release archives

It doesn't make much sense to remove all .gitignore files just to explain users that they should create those files if they want to manage their website using a Git repository.

.build/create-release.sh

@@ -49,8 +49,7 @@ composer require --no-update \
     "picocms/pico-theme ^$VERSION_MILESTONE" \
     "picocms/pico-deprecated ^$VERSION_MILESTONE"
 
-echo "Removing '.git' directory and '.gitignore' file..."
-rm -f .gitignore
+echo "Removing '.git' directory..."
 rm -rf .git
 
 echo "Removing '.git' directories of dependencies..."