Run checks on all PRs (duckduckgo#1929)

Task/Issue URL: https://app.asana.com/0/0/1205320678425970/f
Tech Design URL:
CC: @ayoy

Description:

This PR updates the PR workflow to run checks on all PRs, not just those targeting specific branches. This is to allow us to more effectively leverage stacked PRs in our workflow, as they currently do not have any checks run against them.

Author: samsymons

.github/workflows/pr.yml

@@ -4,8 +4,6 @@ on:
   push:
     branches: [ develop, "release/**" ]
   pull_request:
-    branches: [ develop, "release/**" ]
-
 
 jobs:
   swiftlint: