[pengfeixx]

fix: drop two stdc++ tree symbols from multimedia symbols

1. sw64 build fails at dh_makeshlibs: two std::_Rb_tree internal instantiations
   (_M_get_insert_hint_unique_pos on the QRhi/DmaBufEglContext map and
   equal_range on the QUrl/SampleRate map) are not exported by the sw_64
   toolchain
2. Follow the 6.8 packaging precedent: the deepin 6.8
   libqt6multimedia6.symbols tracked no std::_Rb_tree @Qt_6_PRIVATE_API
   symbols at all, and built fine on all five architectures
3. They are std::map implementation internals, not Qt ABI surface; on arches
   whose toolchains do emit them, unlisted symbols only produce non-fatal
   dpkg-gensymbols warnings

Log: Fix qt6-multimedia sw64 packaging failure by dropping two
std::_Rb_tree private-API symbols inherited from the salsa 6.11 symbols
template

Influence:

1. Rebuild qt6-multimedia on sw64 and verify dh_makeshlibs passes
2. Confirm the remaining symbols still match on amd64/arm64/loong64/mips64el
3. If another arch trips on the remaining four same-class symbols, drop the
   whole class to fully return to the 6.8 baseline

fix: multimedia 符号表移除两个 stdc++ 树符号

1. sw64 构建在 dh_makeshlibs 失败：两个 std::_Rb_tree 内部实例化符号
   （QRhi/DmaBufEglContext map 的 _M_get_insert_hint_unique_pos 与
   QUrl/SampleRate map 的 equal_range）在 sw_64 工具链下未导出
2. 参考 6.8 打包先例：deepin 6.8 的 libqt6multimedia6.symbols 本就不收录
   任何 std::_Rb_tree @Qt_6_PRIVATE_API 符号，五架构构建均通过
3. 这类符号是 std::map 实现内部，不属于 Qt ABI 表面；在会导出它们的架构上，
   未列出的符号仅产生非致命的 dpkg-gensymbols 警告

Log: 修复 qt6-multimedia 在 sw64 上的打包失败，移除两个从 salsa 6.11
符号模板带入的 std::_Rb_tree 私有 API 符号

Influence:

1. 在 sw64 上重编 qt6-multimedia，确认 dh_makeshlibs 通过
2. 确认 amd64/arm64/loong64/mips64el 上其余符号仍完全匹配
3. 若其他架构再报同类剩余四个符号，整类删除以完全回归 6.8 基线

PMS: TASK-396869

[deepin-ci-robot]

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