git-contrib: drop weird non-breaking spaces

For some reason git shortlog spits out non-breaking spaces, let's remove
that, as for our purposes (inclusion in NEWS) we really want breaking
(i.e. normal) spaces.

tools/meson-git-contrib.sh

@@ -4,4 +4,5 @@ git shortlog -s `git describe --abbrev=0`.. | \
         cut -c8- | \
         sed 's/ / /g' | \
         awk '{ print $$0 "," }' | \
+        sed -e 's/ / /g' | \
         sort -u