[LLDB] Fix test failure introduced by llvm#83234 (llvm#83406)

Missed adding a . in the test check

(cherry picked from commit ee297a7)

Author: svs-quic

lldb/test/API/functionalities/completion/TestCompletion.py

@@ -65,7 +65,7 @@ def do_test_variable_completion(self, command):
         self.complete_from_to(f"{command} fooo.dd", f"{command} fooo.dd")
 
         self.complete_from_to(f"{command} ptr_fooo->", f"{command} ptr_fooo->t")
-        self.complete_from_to(f"{command} ptr_fooo->t", f"{command} ptr_fooo->t.x")
+        self.complete_from_to(f"{command} ptr_fooo->t.", f"{command} ptr_fooo->t.x")
         self.complete_from_to(f"{command} ptr_fooo->dd", f"{command} ptr_fooo->dd")
 
         self.complete_from_to(f"{command} cont", f"{command} container")