Remove codeowners from expected_doxygen_warnings.txt

When warnings are removed from expected_doxygen_warnings.txt, it should
be adequate for the codeowners of the relevant source files to review
the change, and it seems better not to also require the codeowners of
the scripts folder.

(Hopefully, we won't generally be adding to the list of expected doxygen
warnings, but we are expecting to fix some warnings and remove them from
the list.)

Author: John Nonweiler

CODEOWNERS

@@ -59,5 +59,7 @@
 /jbmc/regression/
 
 /scripts/ @diffblue/devops @thk123 @forejtv @peterschrammel
+/scripts/expected_doxygen_warnings.txt
+
 /.travis.yml @diffblue/devops @thk123 @forejtv @peterschrammel
 /appveyor.yml @diffblue/devops @thk123 @forejtv @peterschrammel