Remove sort: pillar

Not sure what it does in the first place

systems/meta/historic.md

@@ -10,7 +10,7 @@ semantic wiki, mathematical web services, and invasive OMDoc editing
 technologies. Furthermore, the group works on the utilization of OMDoc to provide Logic
 Interoperability and to establish scientific Communities of Practice.
  
-{% assign systems = site.pages | where: "layout", "system" | sort: "pillar" | sort: "start_date" %}
+{% assign systems = site.pages | where: "layout", "system" | sort: "start_date" %}
 
 <ul class="collection">
     {% for item in systems %}

systems/meta/orphans.md

@@ -9,7 +9,7 @@ to greener pastures (e.g. when they graduate). We put these systems up for adopt
 students. If you are interested, please contact someone from the KWARC group, we would be
 happy to help you understand the development opportunities and get involved. 
 
-{% assign systems = site.pages | where: "layout", "system" | sort: "pillar" | sort: "start_date" %}
+{% assign systems = site.pages | where: "layout", "system" | sort: "start_date" %}
 
 <ul class="collection">
     {% for item in systems %}