docs: fix typo: s/osdemo/osdemos/

(cherry picked from commit 0371956d66cdc8a1629753fca9cb3cdc49b0d145)
diff --git a/docs/osmesa.html b/docs/osmesa.html
index 629d054..525da4d 100644
--- a/docs/osmesa.html
+++ b/docs/osmesa.html
@@ -26,7 +26,7 @@
 </p>
 
 <p>
-There are several examples of OSMesa in the <code>progs/osdemo/</code>
+There are several examples of OSMesa in the <code>progs/osdemos/</code>
 directory.
 </p>