Use HTTPS upgrade instead of upgrade

Author: meacer

fetch.bs

@@ -3261,7 +3261,7 @@ fails with a network error, it is retried over the original URL.
 <p>The HTTPS upgrading algorithm consists of Upgrade and Fallback algorithms, with the following
 steps:
 
-<h4 id=https-upgrades-upgrade>Upgrade algorithm</h4>
+<h4 id=https-upgrades-upgrade>HTTPS upgrade algorithm</h4>
 
 To <dfn>upgrade an HTTP request</dfn> given a <a for=/>request</a> <var>request</var>, run these
 steps: