t/Hydra/Plugin/gitea.t: explain why we loop a few times

Co-authored-by: Cole Helbling <cole.e.helbling@outlook.com>

t/Hydra/Plugin/gitea.t

@@ -60,6 +60,9 @@ if (!defined($pid = fork())) {
     kill('INT', $pid);
 }
 
+# We expect $ctx{jobsdir}/server.py to create the file at $filename, but the time it
+# takes to do so is non-deterministic. We need to give it _some_ time to hopefully
+# settle -- but not too much that it drastically slows things down.
 for my $i (1..10) {
     if (! -f $filename) {
        diag("$filename does not yet exist");