upgrade Go to 1.26.3 (#27924)

Pick up today's Go toolchain and stdlib vulnerability fixes

Ref: https://groups.google.com/g/golang-announce/c/qcCIEXso47M/m/2bOHLAuTBQAJ

Author: tgross

.changelog/27924.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+build: Update Go toolchain to 1.26.3
+```

.go-version

@@ -1 +1 @@
-1.26.2
+1.26.3

contributing/README.md

@@ -55,7 +55,7 @@ A development environment is supplied via Vagrant to make getting started easier
 
 Developing without Vagrant
 ---
-1. Install [Go 1.26.2+](https://golang.org/) *(Note: `gcc-go` is not supported)*
+1. Install [Go 1.26.3+](https://golang.org/) *(Note: `gcc-go` is not supported)*
 1. Clone this repo
    ```sh
    $ git clone https://github.com/hashicorp/nomad.git

go.mod

@@ -1,6 +1,6 @@
 module github.com/hashicorp/nomad
 
-go 1.26.2
+go 1.26.3
 
 // Pinned dependencies are noted in github.com/hashicorp/nomad/issues/11826.
 replace (

scripts/linux-priv-go.sh

@@ -21,7 +21,7 @@ case $(arch) in
 esac
 
 function install_go() {
-	local go_version="1.26.2"
+	local go_version="1.26.3"
 	local download="https://storage.googleapis.com/golang/go${go_version}.linux-${ARCH}.tar.gz"
 
 	if go version 2>&1 | grep -q "${go_version}"; then

scripts/release/mac-remote-build

@@ -56,7 +56,7 @@ REPO_PATH="${TMP_WORKSPACE}/gopath/src/github.com/hashicorp/nomad"
 mkdir -p "${TMP_WORKSPACE}/tmp"
 
 install_go() {
-  local go_version="1.26.2"
+  local go_version="1.26.3"
   local download=
 
   download="https://storage.googleapis.com/golang/go${go_version}.darwin-amd64.tar.gz"