fix: correct include path in pkg-config file

The pkg-config file was incorrectly specifying the include path as
${includedir}/dtk@DTK_VERSION_MAJOR@/DWidget. This path was too specific
and did not match the actual header file installation structure. The
change updates the Cflags to use the base ${includedir} directory,
allowing the compiler to find the DtkWidget headers in their correct
location.

This fix ensures that projects using pkg-config to locate DtkWidget
headers will find them properly without requiring manual include path
adjustments. The incorrect path was causing compilation failures in
dependent projects.

Influence:
1. Test compilation of projects that depend on DtkWidget using pkg-
config
2. Verify that include directives like #include <DWidget> work correctly
3. Check that both cmake and qmake projects can find DtkWidget headers
4. Test with different DTK versions to ensure version compatibility
5. Verify that existing projects don't break due to include path changes

fix: 修正 pkg-config 文件中的头文件包含路径

pkg-config 文件之前错误地将包含路径指定为 ${includedir}/
dtk@DTK_VERSION_MAJOR@/DWidget。这个路径过于具体，与实际的头文件安装结构
不匹配。此次更改将 Cflags 更新为使用基础的 ${includedir} 目录，使编译器
能够在正确的位置找到 DtkWidget 头文件。

此修复确保使用 pkg-config 定位 DtkWidget 头文件的项目能够正确找到它们，
而无需手动调整包含路径。之前的错误路径导致依赖项目编译失败。

Influence:
1. 测试使用 pkg-config 依赖 DtkWidget 的项目的编译
2. 验证 #include <DWidget> 等包含指令能正常工作
3. 检查 cmake 和 qmake 项目都能正确找到 DtkWidget 头文件
4. 使用不同 DTK 版本测试以确保版本兼容性
5. 验证现有项目不会因包含路径更改而出现问题

Author: 18202781743

misc/DtkWidget.pc.in

@@ -7,5 +7,5 @@ Name: Dtk@DTK_NAME_SUFFIX@Widget
 Description: Deepin Tool Kit Widget library
 Version: @DTK_VERSION@
 Libs: -L${libdir} -ldtk@DTK_NAME_SUFFIX@widget
-Cflags: -I${includedir}/dtk@DTK_VERSION_MAJOR@/DWidget
+Cflags: -I${includedir}
 Requires: dtk@DTK_NAME_SUFFIX@core dtk@DTK_NAME_SUFFIX@gui Qt@QT_VERSION_MAJOR@Core Qt@QT_VERSION_MAJOR@Widgets Qt@QT_VERSION_MAJOR@DBus Qt@QT_VERSION_MAJOR@Network Qt@QT_VERSION_MAJOR@PrintSupport