Remove the holding page for Principal Engineer competencies. (#364)

Author: niksilver

data/levels.yml

@@ -43,9 +43,3 @@
     seeing ill-defined or difficult projects through to completion. They are great at
     spotting issues and helping their team navigate them. Senior 2 engineers have a deep
     understanding and willingness to help others for a particular technology or product.
-
-# Principal Engineer
-- id: principal
-  name: Principal Engineer
-  summary: >
-    TODO