sdl12-compat: CI: maybe fix SDL2 header checkout?

SDL Commits
1 
From 4c5cd1e9bda4398a49567d43a97821acf939bdfc Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Tue, 1 Jun 2021 17:56:15 -0400
Subject: [PATCH] CI: maybe fix SDL2 header checkout?

---
 .github/workflows/main.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 8dae769..47d3faa 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -22,7 +22,7 @@ jobs:
       uses: actions/checkout@v2
       with:
         name: libsdl-org/SDL
-        ref: refs/tags/release-2.0.14
+        ref: release-2.0.14
         path: SDL2
     - name: Get sdl12-compat sources
       uses: actions/checkout@v2