Stop invoking the editor through an interactive shell

This was added in d2ecfb9 / Homebrew/homebrew#12784 to fix a bug repotted in Homebrew/homebrew#12779, but
at that time we were invoking the editor via `system` rather than
`exec`.

Now we are using exec, and running it through an interactive shell seems
to cause other problems, for example, emacs does not suspend/resume
properly.

Fixes Homebrew/homebrew#32328.

Library/Homebrew/utils.rb

@@ -212,7 +212,7 @@ end
 def safe_exec cmd, *args
   # This buys us proper argument quoting and evaluation
   # of environment variables in the cmd parameter.
-  exec "/bin/sh", "-i", "-c", cmd + ' "$@"', "--", *args
+  exec "/bin/sh", "-c", "#{cmd} \"$@\"", "--", *args
 end
 
 # GZips the given paths, and returns the gzipped paths