PRCR - Reduced required reviews for srlabs (#1203)

As requested by @the-right-joyce and @louismerlin, the amount of required reviews from the `srlabs` team has been reduced to 1.

See related discussion: paritytech/pr-custom-review#136 (comment)

Author: Bullrich

.github/pr-custom-review.yml

@@ -26,7 +26,7 @@ rules:
       - min_approvals: 1
         teams:
           - polkadot-review
-      - min_approvals: 2
+      - min_approvals: 1
         teams:
           - srlabs