Remove duplicate done-testing text

Author: m-dango

doc/Language/testing.pod6

@@ -211,37 +211,6 @@ Adding C<plan> gives a true picture of the test:
 Note that leaving the C<done-testing> in place will have no effect on the new test
 results, but it should be removed for clarity.
 
-It is recommended that the C<done-testing> function be removed and replaced
-with a valid C<plan> function when all tests are finalized. Use of C<plan> can help
-detect test failures otherwise not reported because tests were accidentally skipped
-due to bugs in the tests or bugs in the compiler.  For example:
-
-    sub do-stuff {@};
-    use Test;
-    ok .is-prime for do-stuff;
-    done-testing;
-
-    # output:
-    1..0
-
-The above example is where a naive C<done-testing> fails. C<do-stuff()> returned
-nothing and tested nothing, even though it should've returned results to test. But
-the test suite doesn't know how many tests were meant to be run, so it passes.
-
-Adding C<plan> gives a true picture of the test:
-
-    sub do-stuff {@};
-    use Test;
-    plan 1;
-    ok .is-prime for do-stuff;
-
-    # output:
-    1..1
-    # Looks like you planned 1 test, but ran 0
-
-Note that leaving the C<done-testing> in place will have no effect on the new test
-results, but it should be removed for clarity.
-
 =head1 Testing return values
 
 The C<Test> module exports various functions that check the return value of a