feat(components): [el-dialog] remove width validator (#5329)

[purepear]

ElDialog is the only place that isValidWidthUnit is used and it is somewhat restrictive in terms of valid css width values. Because there are many possible non-"number + unit" ways to set the width i think it's better to just remove the validator instead of checking for things like min(...), max(...), clamp(...), calc(...), min-content, max-content, fit-content(...), auto, inherit, initial, etc.

If people think it's better to keep the validator but validate agains all possible css width values just let me know and i'll try to do that instead.

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[github-actions]

[sxzz]

/cc @element-plus/backers