Fix broken links

wiki/src/doc/about/license.mdwn

 [[!meta title="License"]]
 
-Tails is [[Free Software|doc/about/license]]: you can download, use, and
+Tails is [Free Software](https://www.gnu.org/philosophy/free-sw.html): you can download, use, and
 share it with no restrictions.
 
 Tails is released under the GNU/GPL (version 3 or above).

wiki/src/news/who_are_you_helping.mdwn

@@ -3,7 +3,7 @@
 [[!tag announce]]
 
 Tails is being distributed free of charge because we strongly believe that
-[free software is more secure by design](/doc/about/trust#free_software). But
+[[free software is more secure by design|doc/about/trust#free_software]]. But
 also because we think that **nobody should have to pay to be safe while using
 computers**. Unfortunately, Tails cannot stay alive without money as developing
 Tails and maintaining our infrastructure [[has a cost|doc/about/finances]].

wiki/src/support/faq.mdwn

@@ -698,7 +698,7 @@ is limited to the browser.
 
 Tails used to provide a <span class="guilabel">New Identity</span>
 feature, but this feature was not a good solution to
-[[separate contextual identities|about/warning#identities]], as it
+[[separate contextual identities|doc/about/warning#identities]], as it
 was dangerous:
 
 * Already existing connections could stay open.