Remove 'should' from disallowed words list in Jest titles

[MrGVSV]

Description

Removed 'should' from the list of disallowed words. I'm not sure why this was originally disallowed, but I believe it makes for nicer-looking test files. This is because affirmative and negative test cases can use the same conjugations for their verbs, whereas without "should", verbs must switch between conjugations (e.g. ___s ... becoming does not ___ ... vs should ___ ... becoming should not ___ ...).

// WITHOUT
it('renders the component when the flag is enabled', () => {/* ... */});
it('does not render the component when the flag is disabled', () => {/* ... */});
it('creates a new user on submit', () => {/* ... */});
it('does not create a new user on failed submit', () => {/* ... */});

// WITH
it('should render the component when the flag is enabled', () => {/* ... */});
it('should not render the component when the flag is disabled', () => {/* ... */});
it('should create a new user on submit', () => {/* ... */});
it('should not create a new user on failed submit', () => {/* ... */});