Fixed typo in changelog.

debian/changelog

@@ -7,7 +7,7 @@ apt (0.7.20) unstable; urgency=low
   * buildlib/config.{sub,guess}:
     - Renewed. This fixes lintian errors.
   * doc/apt.conf.5.xml, debian/apt-transport-https:
-    - Documented briefly 'APT::https' group of options. (Closes: #507398)
+    - Documented briefly 'Acquire::https' group of options. (Closes: #507398)
     - Applied patch from Daniel Burrows to document 'Debug' group of options.
       (Closes: #457265)
     - Mentioned 'APT::Periodic' and 'APT::Archives' groups of options.