Required API for GIO modules to implement.
This function is run when the module is being unloaded from GIO, to finalize the module.
Since 2.56, this function should be named `g_io_<modulename>_unload`, where `modulename` is the plugin’s filename with the `lib` or `libgio` prefix and everything after the first dot removed, and with `-` replaced with `_` throughout. For example, `libgiognutls-helper.so` becomes `gnutls_helper`. Using the new symbol names avoids name clashes when building modules statically. The old symbol names continue to be supported, but cannot be used for static builds.