Fix xgettext warning
warning: msgid 'Open folder where attachment was saved' is used without plural and with plural.
./widgets/opensavedfilefolderwidget.cpp:26: Here is the occurrence without plural.
./widgets/opensavedfilefolderwidget.cpp:62: Here is the occurrence with plural.
Workaround: If the msgid is a sentence, change the wording of the sentence; otherwise, use contexts for disambiguation.