filters: misc cleanups

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

filters/html-converters/rst2html

@@ -1,2 +1,2 @@
 #!/bin/bash
-rst2html.py --template <(echo -e "%(stylesheet)s\n%(body_pre_docinfo)s\n%(docinfo)s\n%(body)s")
+exec rst2html.py --template <(echo -e "%(stylesheet)s\n%(body_pre_docinfo)s\n%(docinfo)s\n%(body)s")