printing: add migration dates

printing/printer_list.markdown

 # List of public D-PHYS printers after the December 2023 printer migration
 
+## Migration dates
+
+| Building           | Date   |
+| ------------------ | ------ |
+| HPZ                | Dec 01 |
+| HIT                | Dec 04 |
+| HPF                | Dec 18 |
+| HPH, HPK           | Dec 19 |
+| HPP, HPR, HPT, HPV | Dec 21 |
+
+
+## Printers
+
 | Current printer | Replacement | Location   | Model |
 | --------------- | ----------- | ---------- | ----- |
 | p-hez-e-17-7    | p-hez-hp001 | HEZ E 17.7 |  A4   |