docs: fix parameter in api key docs (#323)

Signed-off-by: Michele Dolfi <[email protected]>

Author: dolfim-ibm

docs/configuration.md

@@ -52,7 +52,7 @@ THe following table describes the options to configure the Docling Serve app.
 |  | `DOCLING_SERVE_CORS_ORIGINS` | `["*"]` | A list of origins that should be permitted to make cross-origin requests. |
 |  | `DOCLING_SERVE_CORS_METHODS` | `["*"]` | A list of HTTP methods that should be allowed for cross-origin requests. |
 |  | `DOCLING_SERVE_CORS_HEADERS` | `["*"]` | A list of HTTP request headers that should be supported for cross-origin requests. |
-|  | `DOCLING_SERVE_ENG_API_KEY` | | If specified, all the API requests must contain the header `X-Api-Key` with this value. |
+|  | `DOCLING_SERVE_API_KEY` | | If specified, all the API requests must contain the header `X-Api-Key` with this value. |
 |  | `DOCLING_SERVE_ENG_KIND` | `local` | The compute engine to use for the async tasks. Possible values are `local`, `rq` and `kfp`. See below for more configurations of the engines. |
 
 ### Compute engine

docs/usage.md

@@ -32,7 +32,7 @@ On top of the source of file (see below), both endpoints support the same parame
 
 ### Authentication
 
-When authentication is activated (see the parameter `DOCLING_SERVE_ENG_API_KEY` in [configuration.md](./configuration.md)), all the API requests **must** provide the header `X-Api-Key` with the correct secret key.
+When authentication is activated (see the parameter `DOCLING_SERVE_API_KEY` in [configuration.md](./configuration.md)), all the API requests **must** provide the header `X-Api-Key` with the correct secret key.
 
 ## Convert endpoints