docs(ee/audit): drop unused 'file' value from targetType enum

Pre-flight review of #1582 surfaced a stale 'file' value in the targetType enum on the response schema. No createAudit call site in the codebase writes target.type='file' (verified across every await createAudit() and createAuditAction() call site in packages/ excluding tests). The seven real target.type values are: user, org, api_key, account_join_request, invite, chat, scim_token. All seven are already in the enum after this change.

actorType enum still includes 'api_key' alongside 'user'. This is pre-existing in the doc (not introduced by #1582) and may be aspirational/forward-looking — no current code path writes actor.type='api_key', but the Prisma schema stores actorType as a free-form String so the value is not blocked at the database layer. Reporting only; not changing in this PR to keep the diff scoped to the #1581 issue.

Author: Harsh23Kashyap

docs/docs/configuration/audit-logs.mdx

@@ -228,7 +228,7 @@ curl --request GET "$SOURCEBOT_URL/api/ee/audit?since=2026-08-01T00:00:00Z&until
       },
       "targetType": {
         "type": "string",
-        "enum": ["user", "org", "file", "api_key", "account_join_request", "invite", "chat", "scim_token"]
+        "enum": ["user", "org", "api_key", "account_join_request", "invite", "chat", "scim_token"]
       },
       "sourcebotVersion": {
         "type": "string"