Update PROCESS.md

Co-authored-by: Greg Dennis <gregsdennis@yahoo.com>

PROCESS.md

@@ -80,7 +80,7 @@ can be added at any time as long as it meets all criteria for `STAGE-1` status.
 At this stage, the feature should be seeing real world use. These features MAY
 change or be removed all together based on what we learn from real world usage,
 but anything more than small changes should be extremely rare. Any necessary
-feature experimentation and evolution should have be done in `STAGE-0`.
+feature experimentation and evolution should have been done in `STAGE-0`.
 
 Implementers are encouraged to implement `STAGE-1` features, but are not
 expected to maintain support for previous versions if they change. Users who