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/apex/apex.go b/apex/apex.go
index 4424b22..68ad95e 100644
--- a/apex/apex.go
+++ b/apex/apex.go
@@ -2946,12 +2946,8 @@
 }
 
 // Returns apex's min_sdk_version SdkSpec, honoring overrides
-func (a *apexBundle) MinSdkVersion(ctx android.EarlyModuleContext) android.SdkSpec {
-	return android.SdkSpec{
-		Kind:     android.SdkNone,
-		ApiLevel: a.minSdkVersion(ctx),
-		Raw:      a.minSdkVersionValue(ctx),
-	}
+func (a *apexBundle) MinSdkVersion(ctx android.EarlyModuleContext) android.ApiLevel {
+	return a.minSdkVersion(ctx)
 }
 
 // Returns apex's min_sdk_version ApiLevel, honoring overrides