Adapt documentation to renamed ENABLE_SWAGGER option (#5811)

Updates documentation to account for the renamed ENABLE_SWAGGER_ENDPOINT from  #3572 (commit a74426d631)

Signed-off-by: Peter Colberg <peter@colberg.org>

docs/content/doc/advanced/api-usage.en-us.md

@@ -17,7 +17,7 @@ menu:
 
 ## Enabling/configuring API access
 
-By default, `ENABLE_SWAGGER_ENDPOINT` is true, and
+By default, `ENABLE_SWAGGER` is true, and
 `MAX_RESPONSE_ITEMS` is set to 50.  See [Config Cheat
 Sheet](https://docs.gitea.io/en-us/config-cheat-sheet/) for more
 information.

docs/content/doc/advanced/api-usage.zh-cn.md

@@ -17,7 +17,7 @@ menu:
 
 ## 开启/配置 API 访问
 
-通常情况下， `ENABLE_SWAGGER_ENDPOINT` 默认开启并且参数 `MAX_RESPONSE_ITEMS` 默认为 50。您可以从 [Config Cheat
+通常情况下， `ENABLE_SWAGGER` 默认开启并且参数 `MAX_RESPONSE_ITEMS` 默认为 50。您可以从 [Config Cheat
 Sheet](https://docs.gitea.io/en-us/config-cheat-sheet/) 中获取更多配置相关信息。
 
 ## 通过 API 认证

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -323,7 +323,7 @@ Values containing `#` or `;` must be quoted using `` ` `` or `"""`.
 
 ## API (`api`)
 
-- `ENABLE_SWAGGER_ENDPOINT`: **true**: Enables /api/swagger, /api/v1/swagger etc. endpoints. True or false; default is true.
+- `ENABLE_SWAGGER`: **true**: Enables /api/swagger, /api/v1/swagger etc. endpoints. True or false; default is true.
 - `MAX_RESPONSE_ITEMS`: **50**: Max number of items in a page.
 
 ## i18n (`i18n`)