git-gui: Vertically align textboxes with labels

In git-gui after clicking either on 'Create New Repository' or
'Open Existing Repository' the form elements aren't centered like
they are pretty much everywhere else in the app. At least when ran
on a mac, haven't checked on other platforms.

Using grid instead of pack seems to fix this.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>

lib/choose_repository.tcl

@@ -388,9 +388,7 @@ method _do_new {} {
 		-command [cb _new_local_path]
 	set w_localpath $w_body.where.t
 
-	pack $w_body.where.b -side right
-	pack $w_body.where.l -side left
-	pack $w_body.where.t -fill x
+	grid $w_body.where.l $w_body.where.t $w_body.where.b -sticky ew
 	pack $w_body.where -fill x
 
 	trace add variable @local_path write [cb _write_local_path]
@@ -987,9 +985,7 @@ method _do_open {} {
 		-text [mc "Browse"] \
 		-command [cb _open_local_path]
 
-	pack $w_body.where.b -side right
-	pack $w_body.where.l -side left
-	pack $w_body.where.t -fill x
+	grid $w_body.where.l $w_body.where.t $w_body.where.b -sticky ew
 	pack $w_body.where -fill x
 
 	trace add variable @local_path write [cb _write_local_path]