Fix broken links

Author: connoraird

episodes/4-fortran-unit-test-syntax.md

@@ -357,11 +357,11 @@ end function my_test_params_toString
 
 ## Challenge: Write Fortran unit tests in multiple frameworks.
 
-Take a look at [3-fortran-unit-test-syntax/challenge](https://github.com/UCL-ARC/fortran-unit-testing-exercises/tree/main/episodes/3-fortran-unit-test-syntax/challenge).
+Take a look at [4-fortran-unit-test-syntax/challenge](https://github.com/UCL-ARC/fortran-unit-testing-exercises/tree/main/episodes/4-fortran-unit-test-syntax/challenge).
 
 :::::::::::::::::::::::::::::::: solution
 
-A solution is provided in [3-fortran-unit-test-syntax/solution](https://github.com/UCL-ARC/fortran-unit-testing-exercises/tree/main/episodes/3-fortran-unit-test-syntax/solution).
+A solution is provided in [4-fortran-unit-test-syntax/solution](https://github.com/UCL-ARC/fortran-unit-testing-exercises/tree/main/episodes/4-fortran-unit-test-syntax/solution).
 
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episodes/5-debugging-a-broken-test.md

@@ -196,7 +196,7 @@ This results in the output
 
 ```bash
 $ ctest 
-Test project /Users/connoraird/work/fortran-unit-testing-exercises/episodes/4-debugging-a-broken-test/challenge-1/build-cmake
+Test project /Users/connoraird/work/fortran-unit-testing-exercises/episodes/5-debugging-a-broken-test/challenge-1/build-cmake
     Start 2: pfunit_transpose_tests
 1/1 Test #2: pfunit_transpose_tests ...........   Passed    0.24 sec
 
@@ -449,11 +449,11 @@ end do
 
 ### Challenge 2: Debug and fix a failing test.
 
-Take a look at the [4-debugging-a-broken-test/challenge-1 README.md](https://github.com/UCL-ARC/fortran-unit-testing-exercises/tree/main/episodes/4-debugging-a-broken-test/challenge-1/README.md) in the exercises repository.
+Take a look at the [5-debugging-a-broken-test/challenge-1 README.md](https://github.com/UCL-ARC/fortran-unit-testing-exercises/tree/main/episodes/5-debugging-a-broken-test/challenge-1/README.md) in the exercises repository.
 
 :::::::::::::::::::::::::::::::: solution
 
-A solution is provided in [README-solution.md](https://github.com/UCL-ARC/fortran-unit-testing-exercises/tree/main/episodes/4-debugging-a-broken-test/challenge-1/README-solution.md).
+A solution is provided in [README-solution.md](https://github.com/UCL-ARC/fortran-unit-testing-exercises/tree/main/episodes/5-debugging-a-broken-test/challenge-1/README-solution.md).
 
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episodes/6-testing-parallel-code.md

@@ -134,11 +134,11 @@ end subroutine TestMySrcProcedure
 
 ### Challenge 1: Testing MPI parallel code
 
-Take a look at [5-testing-parallel-code/challenge](https://github.com/UCL-ARC/fortran-unit-testing-exercises/tree/main/episodes/5-testing-parallel-code/challenge) in the exercises repository.
+Take a look at [6-testing-parallel-code/challenge](https://github.com/UCL-ARC/fortran-unit-testing-exercises/tree/main/episodes/6-testing-parallel-code/challenge) in the exercises repository.
 
 :::::::::::::::::::::::::::::::: solution
 
-A solution is provided in [5-testing-parallel-code/solution](https://github.com/UCL-ARC/fortran-unit-testing-exercises/tree/main/episodes/5-testing-parallel-code/solution).
+A solution is provided in [6-testing-parallel-code/solution](https://github.com/UCL-ARC/fortran-unit-testing-exercises/tree/main/episodes/6-testing-parallel-code/solution).
 
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