doc: Remove outdated comment

The removed commit is wrong since v0.21.0.

Author: hebasto

doc/build-windows.md

@@ -103,7 +103,7 @@ Build using:
     cd depends
     make HOST=x86_64-w64-mingw32
     cd ..
-    ./autogen.sh # not required when building from tarball
+    ./autogen.sh
     CONFIG_SITE=$PWD/depends/x86_64-w64-mingw32/share/config.site ./configure --prefix=/
     make
     sudo bash -c "echo 1 > /proc/sys/fs/binfmt_misc/status" # Enable WSL support for Win32 applications.