Generate product variants by default

PRODUCT_PRODUCT_VNDK_VERSION is set to 'current' by default. Now, we
can generate product variants without checking the
PRODUCT_PRODUCT_VNDK_VERSION build variable. Remove reading the
PRODUCT_PRODUCT_VNDK_VERSION variable from soong and generate product
variants by default.

Bug: 302255959
Test: m
Change-Id: I9a9b2076f4367c5ce9a393bbb206f8dee3884bd8

apex/apex_test.go

@@ -3088,10 +3088,7 @@ func TestProductVariant(t *testing.T) {
 			apex_available: ["myapex"],
 			srcs: ["foo.cpp"],
 		}
-	`, android.FixtureModifyProductVariables(func(variables android.FixtureProductVariables) {
-		variables.ProductVndkVersion = proptools.StringPtr("current")
-	}),
-	)
+	`)
 
 	cflags := strings.Fields(
 		ctx.ModuleForTests("foo", "android_product.29_arm64_armv8-a_myapex").Rule("cc").Args["cFlags"])
@@ -10521,6 +10518,7 @@ func TestTrimmedApex(t *testing.T) {
 			min_sdk_version: "29",
 			recovery_available: true,
 			vendor_available: true,
+			product_available: true,
 		}
 		api_imports {
 			name: "api_imports",