[minor] Fix Markdown syntax highlighting of kotlin README

kotlin/README.md

@@ -8,7 +8,7 @@ Here is the guide to its implementation and how it can be improved and tested.
 For interactive Kotlin execution, an instance of `KotlinRepl` is created.
 To set REPL properties (such as classpath, generated classes output directory, max result, etc.),
 pass `KotlinReplProperties` to its constructor. For example:
-```$java
+```java
 KotlinReplProperties replProperties = new KotlinReplProperties()
     .maxResult(1000)
     .shortenTypes(true);
@@ -22,7 +22,7 @@ making the receiver's fields and methods accessible.
 
 To add your variables/functions, extend `KotlinReceiver` class (in separate file), declare your fields and methods, and pass an instance of it to
 `KotlinReplProperties`. Example:
-```$java
+```java
 // In separate file:
 class CustomReceiver extends KotlinReceiver {
     public int myValue = 1 // will be converted to Kotlin "var myValue: Int"
@@ -80,4 +80,4 @@ can not use things like `forEach` because of ambiguity between `Iterable<?>.forE
 (`foreach` from Spark's API does work, though).
 * The scoped mode for Kotlin Spark Interpreter currently has issues with having the same class output directory 
 for different intepreters, leading to overwriting classes. Adding prefixes to generated classes or putting them
- in separate directories leads to `ClassNotFoundException` on Spark executors.
+ in separate directories leads to `ClassNotFoundException` on Spark executors.