RELEASE-PROCEDURE: update the release schedule

docs/RELEASE-PROCEDURE

@@ -83,10 +83,13 @@ Coming dates
 Based on the description above, here are some planned release dates (at the
 time of this writing):
 
-- June 14, 2017 (version 7.54.1)
-- August 9, 2017
-- October 4, 2017
 - November 29, 2017
 - January 24, 2018
 - March 21, 2018
 - May 16, 2018
+- July 11, 2018
+- September 5, 2018
+- October 31, 2018
+- December 26, 2018
+- February 20, 2019
+- April 17, 2019