Update min_sdk_version from SdkSpec to ApiLevel

This relands aosp/2457063. The original change broke T and U since those
branches still contain soong modules of type (kind+level). Those soong
modules have been cleaned up now

Test: Used go/abtd to test T and U branches with this change

Bug: 208456999
Change-Id: I0ef7933c055f88cb512a02108f1173e51156ef1c
diff --git a/java/dex.go b/java/dex.go
index 7b6a99a..4d6aa34 100644
--- a/java/dex.go
+++ b/java/dex.go
@@ -343,7 +343,7 @@
 type compileDexParams struct {
 	flags         javaBuilderFlags
 	sdkVersion    android.SdkSpec
-	minSdkVersion android.SdkSpec
+	minSdkVersion android.ApiLevel
 	classesJar    android.Path
 	jarName       string
 }