Remove files from playground module

Author: LukasLechnerDev

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/playground/fundamentals/1_routines.kt

@@ -0,0 +1,9 @@
+package com.lukaslechner.coroutineusecasesonandroid.playground.fundamentals
+
+// IMPORTANT: The playground functions stopped working with Android Studio Otter,
+// that's why I moved them from the "app" gradle module into a standalone Kotlin library
+// gradle module called playground.
+
+fun main() {
+
+}