i18n: make the translation of -u advice in one go
i18n: make the translation of -u advice in one go

The advice (consider use of -u when read_directory takes too long) is
separated into 3 different status_printf_ln() calls, and which brings
trouble for translators.

Since status_vprintf() called by status_printf_ln() can handle eol in
buffer, we could simply join these lines into one paragraph.

Signed-off-by: Jiang Xin <61b5e6324abee2d58ba2cf49f31c723faf6fd946@gmail.com>
Reviewed-by: Eric Sunshine <8d6e34f987851aa599257d3831a1af040886842f@sunshineco.com>
Reviewed-by: Jonathan Nieder <b57189c5f2fd5b3daf3350a77fde90def1080fa5@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git