manual: reenable "Configuring the Theme" for devices without remote LCD

Commit 0c4f89370d ("[2/4]  get rid of HAVE_LCD_CHARCELLS") missed a
closing brace which disabled the above topic in my Sansa Clip+ manual.

Change-Id: Ic7a104757f258a37628645389dbfa1b6c8499415

manual/advanced_topics/main.tex

@@ -192,6 +192,7 @@ viewport. This is done by adding the following line to the
     \config{remote ui viewport: X,Y,[width],[height],[font],[fgshade],[bgshade]}}}
   \opt{lcd_color}{
     \config{remote ui viewport: X,Y,[width],[height],[font],[fgcolour],[bgcolour]}}
+}
 \\*
 
   Only the first two parameters \emph{have} to be specified, the others can