SDL_mixer: ci: Removed some unused CMake variables.

SDL Commits
1 
From 4c5f85595d5a02fdae787886ad9820ac3624bb83 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Thu, 24 Jul 2025 00:29:10 -0400
Subject: [PATCH] ci: Removed some unused CMake variables.

---
 .github/workflows/main.yml | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 2103b71d..5fe503a4 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -108,13 +108,12 @@ jobs:
         set -- \
           -DCMAKE_POSITION_INDEPENDENT_CODE=ON \
           -DCMAKE_BUILD_TYPE=Release \
-          -DSDLMIXER_FLAC=ON \
           -DSDLMIXER_FLAC_LIBFLAC=ON \
           -DSDLMIXER_GME=ON \
           -DSDLMIXER_MOD_XMP=ON \
           -DSDLMIXER_MP3_MPG123=ON \
           -DSDLMIXER_OPUS=ON \
-          -DSDLMIXER_VORBIS=VORBISFILE \
+          -SDLMIXER_VORBIS_VORBISFILE=ON \
           -DSDLMIXER_STRICT=ON \
           -DSDLMIXER_WERROR=ON \
           -DSDLMIXER_INSTALL_MAN=ON \