Setting gemini-2.5-pro-exp window as per #337 (comment)

Author: xenodium

chatgpt-shell-google.el

@@ -225,7 +225,7 @@ This gets set once for each MODEL, based on a heuristic."
                                          :short-version "2.5-pro-exp"
                                          :path "/v1beta/models/gemini-2.5-pro-exp-03-25"
                                          :token-width 4
-                                         :context-window 2048576)
+                                         :context-window 1048576)
         (chatgpt-shell-google-make-model :version "gemini-2.0-pro-exp"
                                          :short-version "2.0-pro-exp"
                                          :path "/v1beta/models/gemini-2.0-pro-exp"