devapp: update contributor summit signup issue

Change-Id: Id19d7b8130ce89595c05231bbb3cf7d54b20edea
Reviewed-on: https://go-review.googlesource.com/132255
Reviewed-by: Andrew Bonventre <andybons@golang.org>

devapp/gophercon.go

@@ -23,7 +23,7 @@ import (
 	"golang.org/x/build/maintner"
 )
 
-const issueNumGerritUserMapping = 21017 // Special sign-up issue.
+const issueNumGerritUserMapping = 27373 // Special sign-up issue.
 
 // intFromStr returns the first integer within s, allowing for non-numeric
 // characters to be present.