Revert "Update min_sdk_version from SdkSpec to ApiLevel"

Revert submission 2457063

Reason for revert: Broken udc-dev

Reverted changes: /q/submissionid:2457063

Change-Id: Id6349fc1318877044af713c914a0afd437d3d2d5
diff --git a/java/app_import.go b/java/app_import.go
index c1de667..e24e780 100644
--- a/java/app_import.go
+++ b/java/app_import.go
@@ -426,8 +426,8 @@
 	return android.SdkSpecPrivate
 }
 
-func (a *AndroidAppImport) MinSdkVersion(ctx android.EarlyModuleContext) android.ApiLevel {
-	return android.SdkSpecPrivate.ApiLevel
+func (a *AndroidAppImport) MinSdkVersion(ctx android.EarlyModuleContext) android.SdkSpec {
+	return android.SdkSpecPrivate
 }
 
 func (a *AndroidAppImport) LintDepSets() LintDepSets {