Drop expunge_all() call in WebTransactionRequest

We're always getting a clean request_id scoped session, so this
shouldn't be necessary. It shows up in memray traces as allocating
memory that doesn't get freed (which I don't understand, it's
WeakInstanceDict instances).

lib/galaxy/managers/context.py

@@ -159,17 +159,6 @@ class ProvidesAppContext:
         """
         return self.app.model.session
 
-    def expunge_all(self):
-        """Expunge all the objects in Galaxy's SQLAlchemy sessions."""
-        app = self.app
-        context = app.model.context
-        context.expunge_all()
-        # This is a bit hacky, should refctor this. Maybe refactor to app -> expunge_all()
-        if hasattr(app, "install_model"):
-            install_model = app.install_model
-            if install_model != app.model:
-                install_model.context.expunge_all()
-
     def get_toolbox(self):
         """Returns the application toolbox.
 

lib/galaxy/webapps/base/webapp.py

@@ -308,7 +308,6 @@ class GalaxyWebTransaction(base.DefaultWebTransaction, context.ProvidesHistoryCo
         self.user_manager = app[UserManager]
         self.session_manager = app[GalaxySessionManager]
         super().__init__(environ)
-        self.expunge_all()
         config = self.app.config
         self.debug = asbool(config.get("debug", False))
         x_frame_options = getattr(config, "x_frame_options", None)