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/app_import.go b/java/app_import.go
index e24e780..c1de667 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.SdkSpec {
-	return android.SdkSpecPrivate
+func (a *AndroidAppImport) MinSdkVersion(ctx android.EarlyModuleContext) android.ApiLevel {
+	return android.SdkSpecPrivate.ApiLevel
 }
 
 func (a *AndroidAppImport) LintDepSets() LintDepSets {