Do not limit the maximum number of jobs

The maximum number of verification jobs must not be
limited in number but only in time, otherwise the verification
pipeline would stop when there are too many open changes.

This is due to how the Checks integration and API works: once
a change is scheduled for being built is automatically not
returned anymore as pending, causing the job to be considered
as removed. If there are too many open changes and thus too
many removed jobs, the build just started would risk to be
immediately removed because of the automatic mechanism
of discarding old builds.

By removing the limit, prevent that situation to happen.
It will still remove the old builds by time and not by
number of builds anymore.

Change-Id: I68d0b65e015be376420f83ef2ac57373bdb0d44a
diff --git a/jenkins/gerrit-verifier.yaml b/jenkins/gerrit-verifier.yaml
index 2e541ab..909af32 100644
--- a/jenkins/gerrit-verifier.yaml
+++ b/jenkins/gerrit-verifier.yaml
@@ -192,7 +192,6 @@
     project-type: multibranch
     node: master
     days-to-keep: 90
-    number-to-keep: 500
     prune-dead-branches: true
     scm:
       - gerrit: