Update Keras version to 3.8. (#2029)

This is causing `autogen` to fail.

Author: hertschuh

scripts/autogen.py

@@ -32,7 +32,7 @@
 GUIDES_GH_LOCATION = Path("keras-team") / "keras-io" / "blob" / "master" / "guides"
 KERAS_TEAM_GH = "https://github.com/keras-team"
 PROJECT_URL = {
-    "keras": f"{KERAS_TEAM_GH}/keras/tree/v3.7.0/",
+    "keras": f"{KERAS_TEAM_GH}/keras/tree/v3.8.0/",
     "keras_tuner": f"{KERAS_TEAM_GH}/keras-tuner/tree/v1.4.7/",
     "keras_hub": f"{KERAS_TEAM_GH}/keras-hub/tree/v0.18.1/",
     "tf_keras": f"{KERAS_TEAM_GH}/tf-keras/tree/v2.18.0/",