Update docs/tutorial/writing-tests/test-case.rst

Co-authored-by: Pierre Equoy <pierre.equoy@canonical.com>

docs/tutorial/writing-tests/test-case.rst

@@ -591,7 +591,7 @@ Checkbox but this can be, in practice, often hard or impossible.
 For a more principled solution see the the Test Plan Tutorial section.
 
 Let's then modify the job so that it actually does the test and use the template
-filter so that we don't generate tests for interfaces that we know that will
+filter so that we don't generate tests for interfaces that we know will
 not work:
 
 .. code-block:: none