Doc: Fix link to renamed setIncludesSubDomains() method

Fix capitalization of setIncludesSubDomains(). While a it,
make the links explicit, so that qdoc generates warnings if they fail.

Pick-to: 6.5 6.6
Change-Id: I74542c288083ec58f866a616da32bd40fcb3f40a
Reviewed-by: Andreas Eliasson <andreas.eliasson@qt.io>
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

src/network/access/qhstspolicy.cpp

@@ -21,8 +21,8 @@ QT_BEGIN_NAMESPACE
     RFC6797.
 
     You can set expiry time and host name for this policy, and control whether it
-    applies to subdomains, either in the constructor or by calling setExpiry(),
-    setHost() and setIncludesSubdomains().
+    applies to subdomains, either in the constructor or by calling \l setExpiry(),
+    \l setHost() and \l setIncludesSubDomains().
 
     \sa QNetworkAccessManager::setStrictTransportSecurityEnabled()
 */