docs(api): document verification and files on the compare endpoint (#39440)

`GET /repos/{owner}/{repo}/compare/{basehead}` reads `verification` and
`files` (both default true), the same as the commit endpoints do:

```go
verification := ctx.FormString("verification") == "" || ctx.FormBool("verification")
files := ctx.FormString("files") == "" || ctx.FormBool("files")
```

The spec only lists `output`, so generated clients cannot turn either
off. This documents both with the wording the commit endpoints already
use and regenerates the spec.

Co-authored-by: bircni <bircni@icloud.com>

templates/swagger/v1-openapi3.generated.json

@@ -20936,6 +20936,22 @@
               ],
               "type": "string"
             }
+          },
+          {
+            "description": "include verification for every commit (disable for speedup, default 'true')",
+            "in": "query",
+            "name": "verification",
+            "schema": {
+              "type": "boolean"
+            }
+          },
+          {
+            "description": "include a list of affected files for every commit (disable for speedup, default 'true')",
+            "in": "query",
+            "name": "files",
+            "schema": {
+              "type": "boolean"
+            }
           }
         ],
         "responses": {