strfmon: Trim the SPACE from international currency symbol

The international currency symbol (int_curr_symbol) has a mandatory
SPACE character as the last character.

Trim this space after reading it, otherwise this extra space will always
be printed when displaying the int_curr_symbol.

Fixes the output when the international currency format is selected
(%i).

Locale         Format    Before           After
en_US.UTF-8    [%i]      [USD 123.45]     [USD123.45]
fr_FR.UTF-8    [%i]      [123,45 EUR ]    [123,45 EUR]

Note that the en_US.UTF-8 locale states that no space should be printed
between the currency symbol and the value (sep_by_space = 0).

Reviewed by: kib
PR: 267282
Github PR: #619
MFC after: 1 week