renovate: Raise prConcurrentLimit to 10

My primary motivation for doing this is when we have two or so
"stalled" PR's that need further work.  I'd like to be able to have the
other PR's get through and merged in the meantime.

I haven't actually seen many instances where PR's by Renovate would
actually trigger a rebase when another is merged.  I think this is
because the yarn.lock format is nice enough that dependencies are more
or less kept separate from each other.  In package.json, only
neighboring dependency changes seem to be the things that trigger
rebases.

Signed-off-by: Kristofer Rye <[email protected]>

Author: rye

.renovaterc.json

@@ -8,7 +8,7 @@
       "after 5pm on every weekday"
     ]
   },
-  "prConcurrentLimit": 5,
+  "prConcurrentLimit": 10,
   "timezone": "America/Chicago",
   "ignoreDeps": [
     "flow-bin",