Unify the strings for Erase eSIM / eUICC

erase_sim_confirm_button & erase_euicc_data_button are the same string
and with same meanings, but since the description of
erase_euicc_data_button is wrong and causes translate issue, clean up
erase_euicc_data_button then.

Fix: 279600315
Test: Visual check on Erase eSIMs dialog
Change-Id: I5dec3dd5c1e851f84dd401dddd5416a27cb1a428