[SHELL32] ro-RO.rc Improvement (reactos#6844)

Addendum to reactos#6517 (the rules) and
Addendum to reactos#6657 (Andreis recent shell32 PR)

Following the rule:

1.) We use only the correct Romanian language diacritics.
This means using lowercase ţ instead of ț.
This means using lowercase ş instead of ș.
This means using uppercase Ş instead of Ș.
Some of XP/2k3sp2 fonts do lack ț and ș and Ș.

2.) Avoid the word "calculator" for the shutdown/logoff prompt (same as Andrei Miloiu did before in his PR at many locations).
Using "sistem" is fine, and using "computer" is fine.

3.) Harmonize some strings used for some FILEOPENDLG_FILTER.

TODO:
[] In a future PR we will have to do the same character replacements for the Shell folder path default values. This has to be done in sync with dll/win32/userenv/lang therefore I left them out here for now, for easier reviewability of those more delicate parts.