DOC: move summit dates to subtitle (#617)

* DOC: move summit dates to subtitle

* DOC: fix yaml whitespace

Author: bsipocz

content/summits/developer/2023/_index.md

@@ -1,6 +1,8 @@
 ---
 title: 2023 Developer Summit
-subtitle: The First Scientific Python Developer Summit
+subtitle: |
+  The First Scientific Python Developer Summit
+  22-26 May 2023 -- Seattle, WA
 summary: |
   The first Scientific Python Developer Summit (May 22-26, 2023) will be hosted by the eScience Institute at the University of Washington. The week-long summit will bring together forty participants, who will develop shared infrastructure for libraries in the Scientific Python ecosystem.
 authors: ["Brigitta Sipőcz", "K. Jarrod Millman", "Stéfan van der Walt"]

content/summits/developer/2024/_index.md

@@ -1,6 +1,8 @@
 ---
-title: 2024 Developer Summit – June 3-5 – Seattle, WA
-subtitle: The Second Scientific Python Developer Summit
+title: 2024 Developer Summit
+subtitle: |
+  The Second Scientific Python Developer Summit
+  3-5 June 2024 – Seattle, WA
 summary: |
   The second Scientific Python Developer Summit (June 3-5, 2024) will be hosted by the eScience Institute at the University of Washington. The week-long summit will bring together forty participants, who will develop shared infrastructure for libraries in the Scientific Python ecosystem.
 authors: ["Brigitta Sipőcz", "K. Jarrod Millman", "Stéfan van der Walt"]