.checkpackageignore: remove package/urandom-scripts/S20urandom

Commit 4a6f9d2516820c296a8af788b259ca96926cd60d removed
package/urandom-scripts/S20urandom but didn't remove it from
.checkpackageignore. Do so now.

The commit actually renamed it to S20seedrng, but it also fixed the
Variables errors so it no longer needs to be ignored.

Signed-off-by: Arnout Vandecappelle <arnout@mind.be>

.checkpackageignore

@@ -169,7 +169,6 @@ package/tvheadend/S99tvheadend Indent Shellcheck Variables
 package/unbound/S70unbound Shellcheck
 package/unscd/S46unscd Indent Shellcheck Variables
 package/upmpdcli/S99upmpdcli Indent Shellcheck Variables
-package/urandom-scripts/S20urandom Variables
 package/usbguard/S20usbguard Indent Shellcheck Variables
 package/vsftpd/S70vsftpd Indent Shellcheck Variables
 package/watchdogd/S01watchdogd Indent NotExecutable