Fix typos in comments and docstrings (#2101)

Found by codespell:
- curent -> current (classes.py)
- suppport -> support, propeties -> properties (inference/__init__.py)
- existance -> existence (inference/analysis.py)
- Propably -> Probably (inference/value/instance.py)

Co-authored-by: maxtaran2010 <ocotifuzo727@gmail.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

jedi/api/classes.py

@@ -831,7 +831,7 @@ class Signature(BaseSignature):
     def index(self):
         """
         Returns the param index of the current cursor position.
-        Returns None if the index cannot be found in the curent call.
+        Returns None if the index cannot be found in the current call.
 
         :rtype: int
         """