Tests of Iterator.prototype.constructor/toStringTag are broken

[Jan Štola]

#3970 updated the following tests (in order to reflect a recent normative change)

built-ins/Iterator/prototype/Symbol.toStringTag/prop-desc.js
built-ins/Iterator/prototype/Symbol.toStringTag/weird-setter.js
built-ins/Iterator/prototype/constructor/prop-desc.js
built-ins/Iterator/prototype/constructor/weird-setter.js

Unfortunately, these tests are broken now.

prop-desc.js tests use verifyConfigurable() that deletes the tested property. So, the subsequent assertions fail. verifyConfigurable() must be the last statement of the test (if used at all).

weird-setter.js tests pass too few arguments to assert.throws() i.e. they fail to specify the type of the expected error.

[Kevin Gibbons]

cc @michaelficarra

[Michael Ficarra]

Opened #3996.