to be consistent in naming.
Backport of Core PR16822 - part 1 of 3
Commit https://github.com/bitcoin/bitcoin/pull/16822/commits/43aa9b0d790840e30c1cd128e67946ffcbfeb721
Note: on our side the spelling of the method name askPassphrase was already good
when it was first backported (see D7105)