require go 1.26.5

setup-go installs exactly the version in the go directive, so the CI
toolchain was 1.26.2 and govulncheck reported five standard library
vulnerabilities reachable from server.Serve, cli fetches and pgx dialing
(GO-2026-5037, GO-2026-4971, GO-2026-4918 among them). All are fixed in
1.26.3/1.26.4; 1.26.5 is the current release and scans clean.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: Vonng

go.mod

@@ -1,6 +1,6 @@
 module pgext
 
-go 1.26.2
+go 1.26.5
 
 require (
 	github.com/jackc/pgx/v5 v5.10.0