weechatScripts.weechat-matrix-bridge: don't export `olm.lua' as script (#46582)

Loading olm.lua as weechat script with `/script load olm.lua' causes
errors like this:

```
/nix/store/43jbh7yxh8j4gjfzbvpd9clncah5dip1-weechat-matrix-bridge-2018-05-29/lib/ffi.so: undefined symbol: lua_tointeger
```

As `olm.lua' is loaded by `matrix.lua' it doesn't need to be included
manually by the weechat configuration.

pkgs/applications/networking/irc/weechat/scripts/weechat-matrix-bridge/default.nix

@@ -25,7 +25,7 @@ stdenv.mkDerivation {
       --replace "__NIX_LIB_PATH__" "$out/lib/?.so"
   '';
 
-  passthru.scripts = [ "olm.lua" "matrix.lua" ];
+  passthru.scripts = [ "matrix.lua" ];
 
   installPhase = ''
     mkdir -p $out/{share,lib}