treewide: fix redirected urls

According to https://repology.org/repository/nix_unstable/problems, we have a
lot of packages that have http links that redirect to https as their homepage.
This commit updates all these packages to use the https links as their
homepage.

The following script was used to make these updates:

```

curl https://repology.org/api/v1/repository/nix_unstable/problems \
    | jq '.[] | .problem' -r \
    | rg 'Homepage link "(.+)" is a permanent redirect to "(.+)" and should be updated' --replace 's@$1@$2@' \
    | sort | uniq > script.sed

find -name '*.nix' | xargs -P4 -- sed -f script.sed -i
```

pkgs/shells/tcsh/default.nix

@@ -37,7 +37,7 @@ stdenv.mkDerivation rec {
       - history mechanism
       - job control
     '';
-    homepage = http://www.tcsh.org/;
+    homepage = https://www.tcsh.org/;
     license = licenses.bsd2;
     maintainers = with maintainers; [ AndersonTorres ];
     platforms = platforms.linux ++ platforms.darwin;

pkgs/shells/xonsh/default.nix

@@ -37,7 +37,7 @@ python3Packages.buildPythonApplication rec {
 
   meta = with stdenv.lib; {
     description = "A Python-ish, BASHwards-compatible shell";
-    homepage = http://xon.sh/;
+    homepage = https://xon.sh/;
     license = licenses.bsd3;
     maintainers = with maintainers; [ spwhitt vrthra ];
     platforms = platforms.all;