SDL_mixer: Remove ability to do '#include "SDL_mixer.h"'

SDL Commits
1 
From b8e98bf3fde7c55071bed53194de057a9b6c3113 Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Fri, 29 Sep 2023 18:24:50 +0200
Subject: [PATCH] Remove ability to do '#include "SDL_mixer.h"'

This reverts commit b206c4be58e7f3c00a5c9122f73925f75642b66c.
---
 CMakeLists.txt         | 2 --
 cmake/sdl3-mixer.pc.in | 2 +-
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 986034e4..d3852d4b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -263,9 +263,7 @@ endif()
 target_include_directories(${sdl3_mixer_target_name}
     PUBLIC
         "$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>"
-        "$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include/SDL3>"
         "$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>"
-        "$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/SDL3_mixer>"
     PRIVATE
         src
         src/codecs
diff --git a/cmake/sdl3-mixer.pc.in b/cmake/sdl3-mixer.pc.in
index 1ef53e47..b93ee693 100644
--- a/cmake/sdl3-mixer.pc.in
+++ b/cmake/sdl3-mixer.pc.in
@@ -10,4 +10,4 @@ Requires: sdl3 >= @SDL_REQUIRED_VERSION@
 Libs: -L${libdir} -lSDL3_mixer
 Requires.private: @PC_REQUIRES@
 Libs.private: @PC_LIBS@
-Cflags: -I${includedir} -I${includedir}/SDL3_mixer
+Cflags: -I${includedir}