all: release v1.26.0-rc.1

Change-Id: I849df1819bf980fea006516beba4a551696e3811
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/302750
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 72b24ee..3b67598 100644
--- a/internal/version/version.go
+++ b/internal/version/version.go
@@ -52,9 +52,9 @@
 //	10. Send out the CL for review and submit it.
 const (
 	Major      = 1
-	Minor      = 25
+	Minor      = 26
 	Patch      = 0
-	PreRelease = "devel"
+	PreRelease = "rc.1"
 )
 
 // String formats the version string for this module in semver format.