Update Junit 5 link, since it's now default (#3263)

Author: sciencewhiz

source/docs/software/wpilib-tools/robot-simulation/unit-testing.rst

@@ -1,6 +1,6 @@
 # Unit Testing
 
-Unit testing is a method of testing code by dividing the code into the smallest "units" possible and testing each unit. In robot code, this can mean testing the code for each subsystem individually. There are many unit testing frameworks for most languages. Java robot projects have [JUnit 5](https://junit.org/junit5/) available by default, and C++ robot projects have [Google Test](https://github.com/google/googletest/blob/main/docs/primer.md).
+Unit testing is a method of testing code by dividing the code into the smallest "units" possible and testing each unit. In robot code, this can mean testing the code for each subsystem individually. There are many unit testing frameworks for most languages. Java robot projects have [JUnit 5](https://junit.org/) available by default, and C++ robot projects have [Google Test](https://github.com/google/googletest/blob/main/docs/primer.md).
 
 ### Writing Testable Code