git-gui: do not mix -translation binary and -encoding

git-gui: do not mix -translation binary and -encoding

git-gui has many instances of '-translation binary' and '-encoding
$SOMETHING' on the same channel.  As eofchar is always null given a
prior commit, the net effect of having '-translation binary' in such
configuration is only to change how text line endings are handled.

For cases where the channel is opened to be consumed via gets, the eol
translation is irrelevant because Tcl's gets is documented to recognize
any of \n, \r, and \r\n as a line ending.  So, keep only the '-encoding
$SOMETHING' configuration in these cases, making the configuration more
clear.

Signed-off-by: Mark Levedahl <mlevedahl@gmail.com>