Changed label for serach bar in ledger from "Search" to "Filter"

The field is actually more filter than search.

This also fixes the bug "In Ledger: Keyboard shortcut for Search (Alt-E)
does not work".

I could not change the label in scheduled transactions view because it
is hard coded in the library. But this should be done as well.

BUG: 338296
FIXED-IN: 4.7.2
REVIEW: 121803