remove unused arg

Author: adamzip

src/Microsoft.DotNet.Darc/DarcLib/VirtualMonoRepo/JsonFileMerger.cs

@@ -83,8 +83,7 @@ public async Task<bool> MergeJsonsAsync(
                 sourceCurrentJson,
                 targetRepo.Path,
                 targetRepoJsonRelativePath,
-                targetRepoCurrentRef,
-                allowMissingFiles))
+                targetRepoCurrentRef))
         {
             hasChanges = true;
         }

src/Microsoft.DotNet.Darc/DarcLib/VirtualMonoRepo/VmrVersionFileMerger.cs

@@ -31,8 +31,7 @@ protected async Task<bool> DeleteFileIfRequiredAsync(
         string sourceRepoCurrentJson,
         NativePath repoPath,
         string filePath,
-        string targetRepoCurrentRef,
-        bool allowMissingFiles)
+        string targetRepoCurrentRef)
     {
         if (sourceRepoPreviousJson != JsonFileMerger.EmptyJsonString
             && sourceRepoCurrentJson == JsonFileMerger.EmptyJsonString