fix: correct typo in README regarding the complaint about automated tests

Author: rubenpenap

exercises/04.performance/README.mdx

@@ -2,7 +2,7 @@
 
 <EpicVideo url="https://www.epicweb.dev/workshops/advanced-vitest-patterns/performance/04-00-introduction" />
 
-The second most common complain about automated tests (after them being flaky, of course) is that they are _slow_. And while flakiness often has a more unpredictable nature, performance issues with tests are more similar to a snowball. They might be there from the start but you won't notice them while having ten tests. They will become painfully apparent once you have a hundred.
+The second most common complaint about automated tests (after them being flaky, of course) is that they are _slow_. And while flakiness often has a more unpredictable nature, performance issues with tests are more similar to a snowball. They might be there from the start but you won't notice them while having ten tests. They will become painfully apparent once you have a hundred.
 
 **I don't want you to be punished for improving the test coverage of your software**. Neither do I want you to be left in the dark when you stare at a 10-minute long test run on CI and begin to question the rationale of your life's choices.