update: remove Kotlin 1.3 references

Mentioning 1.3 seems less than useful at this point.

examples/01_introduction/01_Hello world.md

@@ -9,14 +9,6 @@ fun main() {                        // 2
 ```
 
 1. Kotlin code is usually defined in packages. Package specification is optional: If you don't specify a package in a source file, its content goes to the default package.
-2. An entry point to a Kotlin application is the `main` function. Since Kotlin 1.3, you can declare `main` without any parameters. The return type is not specified, which means that the function returns nothing. 
-3. `println` writes a line to the standard output. It is imported implicitly. Also note that semicolons are optional.
-
-In Kotlin versions earlier than 1.3, the `main` function must have a parameter of type `Array<String>`.
-
-```run-kotlin
-fun main(args: Array<String>) {
-    println("Hello, World!")
-}
-```
+2. An entry point to a Kotlin application is the `main` function. You can declare it without any parameters. The return type is not specified, which means that the function returns nothing. 
+3. `println` writes a line to the standard output. It is imported implicitly. Also, note that semicolons at the end of code lines are optional.