Fix typos in org.springframework.boot.test.context.assertj package

[sbrannen]

The following classes have a copy-n-paste typo of the form "used to decorate and existing".

• AssertableWebApplicationContext
• AssertableReactiveWebApplicationContext
• AssertableApplicationContext
• ApplicationContextAssertProvider

[wilkinsona]

Well spotted, @sbrannen. And thanks for the report.

[sbrannen]

no problem, and thanks for the turbo quick fix. 😉