[editorial] Fix typo (#616)

Author: antosart

index.bs

@@ -4902,7 +4902,7 @@ this algorithm returns normally if compilation is allowed, and throws a
     or event handler needs to be encoded using <a>UTF-8 encode</a> before computing
     its hash. [[SRI]] computes the hash on the raw resource that is being
     fetched instead. This means that it is possible for the hash needed to allow
-    an inline script block to be different that the hash needed to allow an
+    an inline script block to be different from the hash needed to allow an
     external script even if they have identical contents.
 
     <div class="example">