Fix typo in MockitoBeanOverrideHandlerTests

[Leehwajung]

Fix minor typo in MockitoBeanOverrideHandlerTests.java

[sbrannen]

Hi @Leehwajung,

Congratulations on submitting your first PR for the Spring Framework! 👍

We typically do not accept PRs with such small change sets. Rather, we prefer to address multiple related issues in a single PR.

For this particular scenario, I assumed there were likely multiple places across the code base where we could make such changes.

To find those, I used the regular expression \b(\w+)\s+\1\b[^(}], and I committed a22d204, 6bc1968, and 7095f4c to address such "duplicate words" across the code base and documentation.

In light of the above, I am closing this PR.

Thanks anyway for the PR!

Sam