Merge #17239: doc: Changed miniupnp links to https

6f68523 doc: Changed miniupnp links to https (Marius Kjærstad)

Pull request description:

  doc: Changed miniupnp links to https

ACKs for top commit:
  fjahr:
    ACK 6f68523
  fanquake:
    ACK 6f68523 - as mentioned in this [comment](bitcoin/bitcoin#17166 (comment)), in future, there's no need to open a new PR instead than squashing. One of the requirements of contributing to Bitcoin Core is some basic `git` usage, and we have some documentation on that in our [CONTRIBUTING.md](https://github.com/bitcoin/bitcoin/blob/master/CONTRIBUTING.md#squashing-commits) (which also mentions not to open multiple PRs).

Tree-SHA512: 1e806326552b94dc1c2f105bed822a1dd56127d42bbb0c15a16623ff084b2047331f2f1ad5303c99b0d68c70ad2caf8e8028eb354ba4379973b9e1198676ce72

Author: fanquake

doc/build-unix.md

@@ -163,8 +163,8 @@ symbols, which reduces the executable size by about 90%.
 miniupnpc
 ---------
 
-[miniupnpc](http://miniupnp.free.fr/) may be used for UPnP port mapping.  It can be downloaded from [here](
-http://miniupnp.tuxfamily.org/files/).  UPnP support is compiled in and
+[miniupnpc](https://miniupnp.tuxfamily.org) may be used for UPnP port mapping.  It can be downloaded from [here](
+https://miniupnp.tuxfamily.org/files/).  UPnP support is compiled in and
 turned off by default.  See the configure options for upnp behavior desired:
 
 	--without-miniupnpc      No UPnP support miniupnp not required