Fix regex

Author: JoeRobich

src/dotnet-roslyn-tools/PRFinder/Hosts/GitHub.cs

@@ -194,7 +194,7 @@ protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage
 
     [GeneratedRegex(@"^Merge pull request #\d+ from dotnet/merges/")]
     private static partial Regex IsGitHubReleaseFlowCommit();
-    [GeneratedRegex(@"^[automated] Merge branch '.*' => '.*' \(#\d+\)")]
+    [GeneratedRegex(@"^\[automated\] Merge branch '.*' => '.*' \(#\d+\)")]
     private static partial Regex IsGitHubActionCodeFlowCommit();
     [GeneratedRegex(@"^Merge pull request #(\d+) from")]
     private static partial Regex IsGitHubMergePRCommit();