Switch the installer URL to GitHub

It likely can handle global downloads better then we do.

We still host everything on repo.msys2.org as before, so nothing changes there.

Author: lazka

web/index.md

@@ -35,10 +35,10 @@ MSYS2 and what for.
 
 ## Installation
 
-1. Download the installer: <a href="https://repo.msys2.org/distrib/x86_64/msys2-x86_64-20210604.exe" class="button">msys2-x86_64-20210604.exe</a>
+1. Download the installer: <a href="https://github.com/msys2/msys2-installer/releases/download/2021-06-04/msys2-x86_64-20210604.exe" class="button">msys2-x86_64-20210604.exe</a>
 
     <span style="opacity: 0.6;">Verify with SHA256 checksum `2e9bd59980aa0aa9248e5f0ad0ef26b0ac10adae7c6d31509762069bb388e600`
-    or [GPG signature](https://repo.msys2.org/distrib/x86_64/msys2-x86_64-20210604.exe.sig)
+    or [GPG signature](https://github.com/msys2/msys2-installer/releases/download/2021-06-04/msys2-x86_64-20210604.exe.sig)
     by [0xf7a49b0ec](http://keyserver.ubuntu.com/pks/lookup?search=0x0ebf782c5d53f7e5fb02a66746bd761f7a49b0ec&fingerprint=on&op=vindex).</span>
 
 2. Run the installer. MSYS2 requires 64 bit Windows 7 or newer.