Use `kotlin_lang_version` instead of `-lanuage-version`.

The `-language-version` flag is now banned in favor of the soong
parameter `kotlin_lang_version`.

Bug: 383569207
Flag: EXEMPT no-op change
Test: built system image
Change-Id: I40fea86b60c53b39f5498bcf4a9a1b98c06f12e1
diff --git a/Android.bp b/Android.bp
index 4b9d65d..a2edf93 100644
--- a/Android.bp
+++ b/Android.bp
@@ -67,7 +67,6 @@
         "kotlinx-coroutines-android-annotation-stubs",
     ],
     kotlincflags: [
-        "-language-version 2.0",
         "-Xmulti-platform",
         "-opt-in=kotlin.RequiresOptIn",
         "-opt-in=kotlin.experimental.ExperimentalTypeInference",
@@ -82,6 +81,7 @@
         "//apex_available:platform",
         "//apex_available:anyapex",
     ],
+    kotlin_lang_version: "2",
 }
 
 // Expose the host library to Android targets. This is generally an unsafe operation; in using