8199705: Docs.gmk needs to be updated to remove the -html5 option

Reviewed-by: erikj

make/Docs.gmk

@@ -108,7 +108,7 @@ JAVADOC_DISABLED_DOCLINT := accessibility html missing syntax reference
 # The initial set of options for javadoc
 JAVADOC_OPTIONS := -use -keywords -notimestamp \
     -serialwarn -encoding ISO-8859-1 -docencoding UTF-8 -breakiterator \
-    -splitIndex --system none -html5 -javafx --expand-requires transitive \
+    -splitIndex --system none -javafx --expand-requires transitive \
     --override-methods=summary
 
 # The reference options must stay stable to allow for comparisons across the