Fix Italics

[braughtg]

Change the phrase ",called _spec_s" to "*spec*s" at the end of the sentence "A test typically consists of a series of steps that are automated by the Cypress tests, called _spec_s." in the "End-to-End Tests" section under the "Cypress" heading in the ONBOARDING.md file. The _spec_s or *spec*s is supposed to make the spec appear in italics. However, it turns out that * works within a word but _ does not.