fix semicolon → colon in text

Author: schultzdavid

doc/Language/js-nutshell.rakudoc

@@ -62,7 +62,7 @@ between the two languages in greater detail.
 
 =head2 Variables
 
-Variables in Node.js can be defined like this;
+Variables in Node.js can be defined like this:
 
 =begin code :lang<javascript>
 var   foo = 1;  // Lexically scoped with functions and modules