Fix size of step inputs in Chrome

[axelboc]

Fix #1433

@walesch-yan can you please double check? I'm remote and can't run MXCuBE-Web on my Windows machine. Otherwise, I can investigate tomorrow.

[walesch-yan]

This did not solve it

[axelboc]

Ok, strange. I'll look at it tomorrow, then. The styles of the MotorInput need a deeper clean-up, I think.

[axelboc]

Turns out Chrome just ignores the size attribute on the input...

[fabcor-maxiv]

But what kind of <input> is that? Not all of them have the size attribute. Or am I misunderstanding things?

https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input#size

[axelboc]

Wow you're right, it's not valid for number inputs. Why it isn't, I don't understand. Anyways, well spotted! 🎣

I've removed the size attribute and used an em width in the CSS. I've done the same in BeamlineAttributeForm.