doc: add http.ClientRequest maxHeadersCount

In http.ClientRequest's doc, add maxHeadersCount as a public property.
And in the description of server's one, change a hyphen to a comma.

PR-URL: #20361
Refs: #20359
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Author: darai0512

doc/api/http.md

@@ -607,6 +607,12 @@ const setCookie = request.getHeader('set-cookie');
 // setCookie is of type string[]
 ```
 
+### request.maxHeadersCount
+
+* {number} **Default:** `2000`
+
+Limits maximum response headers count. If set to 0, no limit will be applied.
+
 ### request.removeHeader(name)
 <!-- YAML
 added: v1.6.0
@@ -933,7 +939,7 @@ added: v0.7.0
 
 * {number} **Default:** `2000`
 
-Limits maximum incoming headers count. If set to 0 - no limit will be applied.
+Limits maximum incoming headers count. If set to 0, no limit will be applied.
 
 ### server.setTimeout([msecs][, callback])
 <!-- YAML