chore: ignore updates of whatwg-url >=13

whatwg-url@13's minimum-supported Node.js version (MSNV) is Node.js 16.
api-ts still supports Node.js 14, so whatwg-url@13 is incompatible with
api-ts right now.

This commit silences dependabot alerts to update whatwg-url to version
13 or higher. When api-ts' MSNV is 16, we will revert this diff.

Author: ericcrosson-bitgo

.github/dependabot.yml

@@ -34,3 +34,5 @@ updates:
         versions: ['>=16']
       - dependency-name: typescript
         versions: ['>4.8']
+      - dependency-name: whatwg-url
+        versions: ['>=13']