Clarify a text about what the Share button does

As other user wrote, the text of the Share button can be misunderstood. That
text can be changed, this merge request uses an alternative written by Nate
Graham (https://www.phoronix.com/forums/forum/software/desktop-linux/
1343956-kde-plasma-5-26-sees-more-features-fixes-ahead-of-beta?p=1344061#
post1344061).

Revision: plasma/discover!395