Remove some outdated make test invocation suggestions

These should be meson.

Change-Id: I03687b8b03f50fb1684e7ffcd487be855052d6c2

src/libutil/error.cc

@@ -132,7 +132,7 @@ static std::string indent(std::string_view indentFirst, std::string_view indentR
 /**
  * A development aid for finding missing positions, to improve error messages. Example use:
  *
- *     NIX_DEVELOPER_SHOW_UNKNOWN_LOCATIONS=1 _NIX_TEST_ACCEPT=1 make tests/lang.sh.test
+ *     NIX_DEVELOPER_SHOW_UNKNOWN_LOCATIONS=1 _NIX_TEST_ACCEPT=1 just test --suite installcheck -v functional-lang
  *     git diff -U20 tests
  *
  */

tests/functional/lang.sh

@@ -155,7 +155,7 @@ else
         echo ''
         echo 'You can rerun this test with:'
         echo ''
-        echo '    _NIX_TEST_ACCEPT=1 make tests/functional/lang.sh.test'
+        echo '    _NIX_TEST_ACCEPT=1 just test --suite installcheck -v functional-lang'
         echo ''
         echo 'to regenerate the files containing the expected output,'
         echo 'and then view the git diff to decide whether a change is'