doc: fix outgoingMessage.removeHeader() signature

Specify that `outgoingMessage.removeHeader()` takes a `name` argument
whose type is string.

PR-URL: #42652
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Akhil Marsonya <akhil.marsonya27@gmail.com>

doc/api/http.md

@@ -2641,12 +2641,14 @@ it inherits from `Stream`.
 
 The User should not call this function directly.
 
-### `outgoingMessage.removeHeader()`
+### `outgoingMessage.removeHeader(name)`
 
 <!-- YAML
-added:  v0.4.0
+added: v0.4.0
 -->
 
+* `name` {string} Header name
+
 Removes a header that is queued for implicit sending.
 
 ```js