Fix comments documenting the alternative title page

Signed-off-by: Leonid Bloch <leonid.bloch@esrf.fr>

ESRF_presentation_template.tex

@@ -40,7 +40,7 @@
 \begin{frame}[t]{Alternative title/subtitle page}
 % Alternative title page
 % Receives content (single image MUST BE 500X800 OR ANY 5X8 ASPECT RATIO), a background color, a text color, and a text.
-% Usage: \AlterTitPage{IMAGE WITHOUT THE FILE EXTENSION}{COLOR FOR TEXTBOX}{TEXT}
+% Usage: \AlterTitPage{IMAGE OBJECT}{COLOR FOR TEXTBOX}{COLOR FOR TEXT}{TEXT}
 \AlterTitPage{\includegraphics[height=0.744\paperheight]{ESRF-img}}{ESRFblue2}{white}{
 \begin{center}
   \vskip2.5em