all: release v1.26.0

Change-Id: I15ecd5b768516fd2382cfbc8b337ad3d8817deab
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/302752
Trust: Joe Tsai <joetsai@digital-static.net>
Reviewed-by: Damien Neil <dneil@google.com>
diff --git a/internal/version/version.go b/internal/version/version.go
index b5be599..5879131 100644
--- a/internal/version/version.go
+++ b/internal/version/version.go
@@ -54,7 +54,7 @@
 	Major      = 1
 	Minor      = 26
 	Patch      = 0
-	PreRelease = "rc.1.devel"
+	PreRelease = ""
 )
 
 // String formats the version string for this module in semver format.