Update spec/index.html

Co-authored-by: Ted Thibodeau Jr <[email protected]>

Author: pchampin

spec/index.html

@@ -1992,7 +1992,7 @@ <h2>Security Considerations</h2>
   <p>RDF can express data which is presented to the user, such as RDF Schema labels.
     Applications rendering <a>strings</a> retrieved from untrusted RDF documents,
     or using unescaped characters,
-    are encouraged to use warnings and other appropriate means to limit the possibility
+    ought to use warnings and other appropriate means to limit the possibility
     that malignant strings might be used to mislead the reader.
     The security considerations in the media type registration for XML ([[RFC3023]] section 10)
     provide additional guidance around the expression of arbitrary data and markup.</p>