Renamed kotlinx-serialization-runtime to kotlinx-serialization-core (#953)

Also bumped version to 1.0-M2
diff --git a/integration-test/build.gradle b/integration-test/build.gradle
index 75ff64f..4cb6d16 100644
--- a/integration-test/build.gradle
+++ b/integration-test/build.gradle
@@ -58,7 +58,7 @@
         commonMain {
             dependencies {
                 implementation kotlin('stdlib-common')
-                implementation "org.jetbrains.kotlinx:kotlinx-serialization-runtime:$serialization_version"
+                implementation "org.jetbrains.kotlinx:kotlinx-serialization-core:$serialization_version"
                 implementation "org.jetbrains.kotlinx:kotlinx-serialization-protobuf:$serialization_version"
                 implementation "org.jetbrains.kotlinx:kotlinx-serialization-cbor:$serialization_version"
             }