[PATCH kexec-tools] workflow: update to use checkout at v4

[Simon Horman]

Update to use checkout at v4.

This addresses the following warning that appears in GitHub runs:

"Node.js 16 actions are deprecated. Please update the following actions
 to use Node.js 20: actions/checkout at v3. For more information
 see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

Link: https://github.com/horms/kexec-tools/actions/runs/7753454923
Signed-off-by: Simon Horman <horms at kernel.org>
---
 .github/workflows/build.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index d0007f14b274..46edde66e384 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -28,7 +28,7 @@ jobs:
             libxen: libxen
     steps:
     - name: Checkout
-      uses: actions/checkout at v3
+      uses: actions/checkout at v4
 
     - name: Set Environment
       env: