git: don't ask canMerge in acceptFileRevision in MultipleFilesMergeDialog

Follow-up to fc52239

This commit is made for consistency: if we use canMerge to check if the Merge button can be pressed, then it should be so for both MergeSession implementations.

platform/vcs-impl/src/com/intellij/openapi/vcs/merge/MultipleFileMergeDialog.kt

@@ -274,8 +274,6 @@ open class MultipleFileMergeDialog(
   }
 
   private fun acceptFileRevision(file: VirtualFile, resolution: MergeSession.Resolution) {
-    if (mergeSession?.canMerge(file)  == false) return
-
     if (!DiffUtil.makeWritable(project, file)) {
       throw IOException("File is read-only: " + file.presentableName)
     }