fix: issue with bit check in from_be_bytes

[madztheo]

Description

Fixes an issue with the from_be_bytes preventing the use of the function when the number of bits of the bytes passed as argument is the same as the number of bits encoding the modulus.

Problem*

fn from_be_bytes<let NBytes: u32>(x: [u8; NBytes]) -> BigNum<N, Params> {
        let num_bits = NBytes * 8;
        let modulus_bits = Params::modulus_bits();
        assert(num_bits > modulus_bits);
        assert(num_bits - modulus_bits < 8);
        ...
}

In the original code, when num_bits yields the same value as modulus_bits the assert fails and the function is usuable.

Summary*

As this behavior is not desired, simply replacing the strictly greater than with a greater than or equal fixes the issue:

fn from_be_bytes<let NBytes: u32>(x: [u8; NBytes]) -> BigNum<N, Params> {
        let num_bits = NBytes * 8;
        let modulus_bits = Params::modulus_bits();
        assert(num_bits >= modulus_bits);
        assert(num_bits - modulus_bits < 8);
        ...
}

Which is what this PR changes.

Additional Context

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.