Ensure clients get write capability (#10872)

When Ydoc requests to open file and encounters a timeout, it will
attempt to retry the request. At least that's the behaviour since
 #10787.
Unfortunately, the write lock on the file might be already held and
identified by the client id and actor reference. The latter is always
determined by the request and therefore spurious. The same client should
always be given the same capability, even on retries.

engine/language-server/src/main/scala/org/enso/languageserver/text/CollaborativeBuffer.scala

@@ -914,10 +914,12 @@ class CollaborativeBuffer(
     autoSave: Map[ClientId, (ContentVersion, Cancellable)]
   ): Unit = {
     val writeCapability =
-      if (lockHolder.isEmpty)
-        Some(CapabilityRegistration(CanEdit(bufferPath)))
-      else
+      lockHolder match {
+        case Some(session) if session.clientId != rpcSession.clientId =>
           None
+        case _ =>
+          Some(CapabilityRegistration(CanEdit(bufferPath)))
+      }
     sender() ! OpenFileResponse(Right(OpenFileResult(buffer, writeCapability)))
     context.become(
       collaborativeEditing(