remove "Known problems" of verbose_bit_mask

[lapla-cogito]

changelog: none

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[lapla-cogito]

I checked this on my x86 machine with the following:

#[no_mangle]
pub fn f(x: i32) -> bool {
    x.trailing_zeros() >= 4 // or `x & 15 == 0`
}

fn main(){}

and compared the output of rustc --emit asm src/main.rs -O. As a result, either way of implementation didn't change the assembly output for f:

f:
	.cfi_startproc
	testb	$15, %dil
	sete	%al
	retq

[llogiq]

Cool! Thank you for checking this out.