Closing signature via PRs for now

Author: ehashman

README.md

@@ -3,7 +3,9 @@ Thanks for volunteering to sign this open letter!
 
 ## How to sign :memo:
 
-To sign, please email digitalautonomy at riseup.net or [submit a pull request](https://github.com/rms-open-letter/rms-open-letter.github.io/pulls).
+To sign, please email digitalautonomy at riseup.net.
+
+**⚠️ As of Mar. 28, 2021 00:00 UTC we are no longer accepting signatures via pull request. You can still send one via email.**
 
 Please add your name in the right place in the list. If you're using the GitHub editor, please ensure that it doesn't renumber everyone. You can do this by going to the first character of the next line, press enter to create a new empty line, then type "1. My Name." Each signature should start with a "1. "