[5.3-alpha] ">& /some/file" would fail when /some/file already exists

[Clark Wang]

(I'm using the "devel" branch as the "bash-5.3-testing" branch failed
to build for me. HEAD: 8c8daff1e3661c)

To reproduce:

$ bash53 --norc
bash53-5.3# touch /tmp/file
bash53-5.3# echo >& /tmp/file
bash53: /tmp/file: File exists
bash53-5.3#