[Metadata] Add missing kotlin metadata file

Bug: b/234559869
Change-Id: Ibc977074739d29c6c0f91178fbe67ffd05fa42c7
diff --git a/src/test/proguard/valid/keep-kotlin-metadata.flags b/src/test/proguard/valid/keep-kotlin-metadata.flags
new file mode 100644
index 0000000..b5a6fcd
--- /dev/null
+++ b/src/test/proguard/valid/keep-kotlin-metadata.flags
@@ -0,0 +1 @@
+-keepkotlinmetadata
\ No newline at end of file