Bump kotlin coroutines from 1.0.0 -> 1.3.6 (#352)

thrifty-runtime-ktx/build.gradle

@@ -26,5 +26,5 @@ apply plugin: 'com.vanniktech.maven.publish'
 dependencies {
     api project(':thrifty-runtime')
     api libraries.kotlin
-    api 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.0.0'
+    api 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.6'
 }