fix: iterator is not pointer

[eagleoflqj]

After upgrading emscripten to 4.0.0, fcitx5 failed to compile:

FAILED: fcitx5/src/lib/fcitx-utils/CMakeFiles/Fcitx5Utils.dir/semver.cpp.o 
/home/runner/work/fcitx5-js/fcitx5-js/emsdk/upstream/emscripten/em++ -DFCITX_GETTEXT_DOMAIN=\"fcitx5\" -DFMT_HEADER_ONLY=1 -DFcitx5Utils_EXPORTS -I/home/runner/work/fcitx5-js/fcitx5-js/build/fcitx5 -I/home/runner/work/fcitx5-js/fcitx5-js/fcitx5/src/lib/fcitx-utils/.. -I/home/runner/work/fcitx5-js/fcitx5-js/build/fcitx5/src/lib/fcitx-utils/.. -isystem /home/runner/work/fcitx5-js/fcitx5-js/build/sysroot/usr/include -Wall -Wextra  -O3 -DNDEBUG -std=c++17 -fPIC -fvisibility=hidden -fvisibility-inlines-hidden -fPIC -fexceptions -MD -MT fcitx5/src/lib/fcitx-utils/CMakeFiles/Fcitx5Utils.dir/semver.cpp.o -MF fcitx5/src/lib/fcitx-utils/CMakeFiles/Fcitx5Utils.dir/semver.cpp.o.d -o fcitx5/src/lib/fcitx-utils/CMakeFiles/Fcitx5Utils.dir/semver.cpp.o -c /home/runner/work/fcitx5-js/fcitx5-js/fcitx5/src/lib/fcitx-utils/semver.cpp
/home/runner/work/fcitx5-js/fcitx5-js/fcitx5/src/lib/fcitx-utils/semver.cpp:36:17: error: variable 'endOfNum' with type 'const auto *' has incompatible initializer of type 'std::__wrap_iter<const char *>'
   36 |     const auto *endOfNum =
      |                 ^
   37 |         std::find_if_not(str.begin(), str.end(), charutils::isdigit);
      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.