Fix vue-select styles

[Pytal]

Fix #35690

Non-breaking version of #35165 which had to be reverted for reasons described in #35665

While each consecutive :not() pseudo-class adds to the specificity of the CSS rule, using a comma-separated list of selectors instead reduces the specificity to that of only the most specific selector in the list, see MDN docs

• Verify that styles of non-NcSelect* components in @nextcloud/vue remain unchanged
• Verify that styles of server settings and files pages remain unchanged

[Pytal]

/backport to stable25

[skjnldsv]

While each consecutive :not() pseudo-class adds to the specificity of the CSS rule, using a comma-separated list of selectors instead reduces the specificity to that of only the most specific selector in the list, see MDN docs

Oooh, I didn't know that! Nice @Pytal
Thanks for the explanations :)