docs: Replace GitFlic URL with official GitHub repository for libmdbx (paradigmxyz#16496)

Author: reject-i

crates/storage/libmdbx-rs/README.md

@@ -13,7 +13,7 @@ Make sure to follow the [building steps](https://libmdbx.dqdkfa.ru/usage.html#ge
 
 ```bash
 # clone libmmdbx to a repository outside at specific tag
-git clone https://gitflic.ru/project/erthink/libmdbx.git ../libmdbx --branch v0.7.0
+git clone https://github.com/erthink/libmdbx.git ../libmdbx --branch v0.7.0
 make -C ../libmdbx dist
 
 # copy the `libmdbx/dist/` folder just created into `mdbx-sys/libmdbx`