all: release v1.20.1

Change-Id: I77c61b55d3c6aa540103ffe82c9dd226959bb753
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/222698
Reviewed-by: Damien Neil <dneil@google.com>
diff --git a/runtime/protoimpl/version.go b/runtime/protoimpl/version.go
index 89990ce..5764b46 100644
--- a/runtime/protoimpl/version.go
+++ b/runtime/protoimpl/version.go
@@ -52,8 +52,8 @@
 const (
 	versionMajor      = 1
 	versionMinor      = 20
-	versionPatch      = 0
-	versionPreRelease = "devel"
+	versionPatch      = 1
+	versionPreRelease = ""
 )
 
 // VersionString formats the version string for this module in semver format.