shutils/update_check.sh: be more strict with rubygem update checks

try to match the whole line from

href="/gems/${pkgname#ruby-}/versions/[VERSION NUMBERS]"

matching until the quote avoids problems like the travis gem that has
special versions like

1.8.10.travis.921.11

before it would match until 1.8.10., now it doesn't match.

common/xbps-src/shutils/update_check.sh

@@ -68,7 +68,7 @@ update_check() {
                 rx='href="\K[\d\.]+(?=/")';;
             *rubygems.org*)
                 url="https://rubygems.org/gems/${pkgname#ruby-}"
-                rx='versions/\K[\d\.]+' ;;
+                rx='href="/gems/'${pkgname#ruby-}'/versions/\K[\d\.]*(?=")' ;;
             esac
         fi