Make parameters to subproject symbol analysis url request optional (#431)

We want the two fields to `subproject_symbol_analysis_url_request` to be
optional rather than encoded as an ADT.

- [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 1.50.0.
See
https://atd.readthedocs.io/en/latest/atdgen-tutorial.html#smooth-protocol-upgrades
	  Note that the types related to the semgrep-core JSON output or the
	  semgrep-core RPC do not need to be backward compatible!
- [x] Any accompanying changes in `semgrep-proprietary` are approved and
ready to merge once this PR is merged

Author: TikhonJelvis

semgrep_output_v1.atd

@@ -3375,8 +3375,8 @@ type upload_subproject_symbol_analysis_params = {
 type subproject_symbol_analysis_url_request
   <doc text="Sent by the CLI to the POST /api/agent/scans/{scan_id}/subproject_symbols_upload_url/">
   = {
-  manifest_path: fpath option;
-  lockfile_path: fpath option;
+  ?manifest_path: fpath option;
+  ?lockfile_path: fpath option;
 }
 
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