Remove $PRINT helper function

The `$PRINT` helper function has no effect on test behavior. The
following tests use it to report assertion outcomes (and as a result
will fail silently):

- test/language/function-code/S10.2.1_A4_T2.js
- test/language/function-code/S10.2.1_A5.1_T1.js
- test/language/function-code/S10.2.1_A5.1_T2.js
- test/language/function-code/S10.2.1_A5.2_T1.js

Remove the function definition and all references within tests. Update
tests that use it as an error reporting mechanism to instead use an
appropriate `assert` helper function.