fix: mark deployment id as mutable (#262)

I forgot to do this :/

- [X] I ran `make setup && make` to update the generated code after
editing a `.atd` file (TODO: have a CI check)
- [X] I made sure we're still backward compatible with old versions of
the CLI.
For example, the Semgrep backend need to still be able to *consume* data
generated
	  by Semgrep 1.17.0.
See
https://atd.readthedocs.io/en/latest/atdgen-tutorial.html#smooth-protocol-upgrades

Author: ajbt200128

semgrep_metrics.atd

@@ -102,7 +102,7 @@ type environment = {
     ~isDiffScan <python default="False"> <ocaml mutable> : bool;
     ?integrationName <ocaml mutable>: string option;
     ~isAuthenticated <python default="False"> <ocaml mutable>: bool;
-    ?deployment_id: int option;
+    ?deployment_id <ocaml mutable>: int option;
   }
 
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