Fix typos in some files

Author: khanhkhanhlele

core/src/main/java/org/apache/calcite/materialize/MutableNode.java

@@ -88,7 +88,7 @@ void flatten(List<MutableNode> flatNodes) {
     }
   }
 
-  /** Returns whether this node is cylic, in an undirected sense; that is,
+  /** Returns whether this node is cyclic, in an undirected sense; that is,
    * whether the same descendant can be reached by more than one route. */
   boolean isCyclic() {
     final Set<MutableNode> descendants = new HashSet<>();

site/_posts/2021-10-19-release-1.28.0.md

@@ -78,7 +78,7 @@ changes needed to be made:
   [`@Value.Immutable`](https://immutables.github.io/immutable.html#value)
   annotation.
 * Where `RelRule.Config` subclasses were nested 2+ classes deep, the
-  interfaces have been marked deprecated and are superceded by new,
+  interfaces have been marked deprecated and are superseded by new,
   uniquely named interfaces. The original Configs extend the new
   uniquely named interfaces. Subclassing these work as before and the
   existing rule signatures accept any previously implemented Config