tests: add missing fe comparison checks for inverse field test cases

`check_fe_equal` is a wrapper around `secp256k1_fe_equal` that takes
care of normalization. Since it doesn't check anything itself, the
CHECK macro is needed at the call-sites to actually ensure equality.

src/tests.c

@@ -3618,9 +3618,9 @@ static void run_inverse_tests(void)
     for (i = 0; (size_t)i < sizeof(fe_cases)/sizeof(fe_cases[0]); ++i) {
         for (var = 0; var <= 1; ++var) {
             test_inverse_field(&x_fe, &fe_cases[i][0], var);
-            check_fe_equal(&x_fe, &fe_cases[i][1]);
+            CHECK(check_fe_equal(&x_fe, &fe_cases[i][1]));
             test_inverse_field(&x_fe, &fe_cases[i][1], var);
-            check_fe_equal(&x_fe, &fe_cases[i][0]);
+            CHECK(check_fe_equal(&x_fe, &fe_cases[i][0]));
         }
     }
     for (i = 0; (size_t)i < sizeof(scalar_cases)/sizeof(scalar_cases[0]); ++i) {