Revert "Additional tests for QuantifiableAssertion" (#1458)

test/language/literals/regexp/invalid-optional-lookbehind.js

...e/literals/regexp/invalid-optional-negative-lookbehind.js

test/language/literals/regexp/invalid-range-lookbehind.js

...uage/literals/regexp/invalid-range-negative-lookbehind.js

...language/literals/regexp/u-invalid-optional-lookbehind.js

.../literals/regexp/u-invalid-optional-negative-lookahead.js

...literals/regexp/u-invalid-optional-negative-lookbehind.js

...guage/literals/regexp/u-invalid-quantifiable-assertion.js

test/language/literals/regexp/u-invalid-range-lookahead.js

test/language/literals/regexp/u-invalid-range-lookbehind.js

...age/literals/regexp/u-invalid-range-negative-lookahead.js

...ge/literals/regexp/u-invalid-range-negative-lookbehind.js