ci/request-reviews: Fix code owner requests for filenames with spaces

Discovered in https://github.com/NixOS/nixpkgs/pull/368656#issuecomment-2564266513

Changed files
+2 -1
ci
request-reviews
+2 -1
ci/request-reviews/get-code-owners.sh
···
for file in "${touchedFiles[@]}"; do
result=$(codeowners --file "$tmp"/codeowners "$file")
-
read -r file owners <<< "$result"
+
# Remove the file prefix and trim the surrounding spaces
+
read -r owners <<< "${result#"$file"}"
if [[ "$owners" == "(unowned)" ]]; then
log "File $file is unowned"
continue