Remove duplicate codeFlavor documentation

One of the 2 identical codeFlavor configuration parameters in the maven plugin docs was removed.

swift-maven-plugin/README.md

@@ -129,14 +129,6 @@ created exceptions are checked exceptions and inherit from <tt>java.lang.Excepti
 
 <tt>extendRuntimeException</tt> is optional, default value is "true".
 
-## codeFlavor
-
-Selects the type of code generated by the plugin. Currently, only two flavors are supported: <tt>java-regular</tt> and <tt>java-immutable</tt>.
-
-<tt>codeFlavor</tt> is optional, default value is "java-regular".
-
-    <codeFlavor>java-immutable</codeFlavor>
-
 # Maven lifecycle
 
 The <tt>generate</tt> goal of the plugin is by default hooked into the <tt>generate-sources</tt> phase of the maven lifecycle.