Drop "license-file" from Cargo.toml

This is an extremely unimportant non-issue but I noticed this while updating the NixOS packaging repository:

> warning: only one of `license` or `license-file` is necessary
> `license` should be used if the package license can be expressed with a standard SPDX expression.
> `license-file` should be used if the package uses a non-standard license.
> See https://doc.rust-lang.org/cargo/reference/manifest.html#the-license-and-license-file-fields for more information.

memflow-win32/Cargo.toml

Lines 11 to 12 in 74bc684

    
           license-file = "LICENSE" 
        
           license = "MIT"

I noticed it, too. Its now removed! Thanks :)