all: start v1.35.1-devel

Change-Id: I67979ea166a3fffba8c303fa1cc47f9eacb606b4
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/618198
Reviewed-by: Lasse Folger <lassefolger@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
diff --git a/internal/version/version.go b/internal/version/version.go
index fb8e15e..a7e0e23 100644
--- a/internal/version/version.go
+++ b/internal/version/version.go
@@ -53,7 +53,7 @@
 	Major      = 1
 	Minor      = 35
 	Patch      = 1
-	PreRelease = ""
+	PreRelease = "devel"
 )
 
 // String formats the version string for this module in semver format.