Exclude NOP and TOPIC tags from inheritance

Those tags are meant to mark the current headline (and nothing below) as either
just a headline (via NOP, i.e., no projects) or as a topic (i.e., a general
obligation and not a concrete thing to achieve).

This tells `org-set-tags-command` to not clear the NOP tag if it's available
somewhere at a parent node – a thing `org-set-tags-command` apparently seems to
be doing in general to keep the tags hierarchy clean.

init.el

@@ -821,6 +821,9 @@
                   ("NOP" . ?o)
                   ("TOPIC" . ?t))
 
+                org-tags-exclude-from-inheritance
+                '("NOP" "TOPIC")
+
                 org-fast-tag-selection-single-key 'expert)
 
           ;; Faces