gapi(test): avoid anonymous namespace types as template parameters

modules/gapi/test/gapi_array_tests.cpp

@@ -240,7 +240,8 @@ TEST(GArray_VectorRef, TestMov)
     EXPECT_EQ(V{}, vtest);
 }
 
-namespace {
+// types from anonymous namespace doesn't work well with templates
+inline namespace gapi_array_tests {
     struct MyTestStruct {
         int i;
         float f;