all: start v1.25.0-devel

Change-Id: Iab5d460374c67a995a5d3058cfbc55e6aaa21b38
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/239378
Reviewed-by: Damien Neil <dneil@google.com>
diff --git a/internal/version/version.go b/internal/version/version.go
index 72cf770..72b24ee 100644
--- a/internal/version/version.go
+++ b/internal/version/version.go
@@ -54,7 +54,7 @@
 	Major      = 1
 	Minor      = 25
 	Patch      = 0
-	PreRelease = ""
+	PreRelease = "devel"
 )
 
 // String formats the version string for this module in semver format.