Revert "IO: ImGuiMod_Shortcut (Ctrl/Cmd depending on platform) is reflected in io.KeyMods. (#5923, #456)"

This reverts commit b8f93a8fe0980cdcd9ec58dd529a4f1daac4a78e. Too breaking for user.

docs/CHANGELOG.txt

@@ -68,7 +68,6 @@ Other changes:
 - ImDrawList: Automatically calling ChannelsMerge() if not done after a split.
 - ImDrawList: Fixed OOB access in _CalcCircleAutoSegmentCount when passing excessively
   large radius to AddCircle(). (#6657, #5317) [@EggsyCRO, @jdpatdiscord]
-- IO: ImGuiMod_Shortcut (Ctrl/Cmd depending on platform) is reflected in io.KeyMods. (#5923, #456)
 - IO: Exposed io.PlatformLocaleDecimalPoint to configure decimal point ('.' or ',') for
   languages needing it. Should ideally be set to the value of '*localeconv()->decimal_point'
   but our backends don't do it yet. (#6719, #2278)

imgui.cpp

@@ -8480,7 +8480,6 @@ static ImGuiKeyChord GetMergedModsFromKeys()
     if (ImGui::IsKeyDown(ImGuiMod_Shift))    { mods |= ImGuiMod_Shift; }
     if (ImGui::IsKeyDown(ImGuiMod_Alt))      { mods |= ImGuiMod_Alt; }
     if (ImGui::IsKeyDown(ImGuiMod_Super))    { mods |= ImGuiMod_Super; }
-    if (ImGui::IsKeyDown(ImGuiMod_Shortcut)) { mods |= ImGuiMod_Shortcut; }
     return mods;
 }
 
@@ -9227,7 +9226,7 @@ static void ImGui::ErrorCheckEndFrameSanityChecks()
     // We silently accommodate for this case by ignoring the case where all io.KeyXXX modifiers were released (aka key_mod_flags == 0),
     // while still correctly asserting on mid-frame key press events.
     const ImGuiKeyChord key_mods = GetMergedModsFromKeys();
-    IM_ASSERT((key_mods == 0 || (g.IO.KeyMods & ~ImGuiMod_Shortcut ) == (key_mods & ~ImGuiMod_Shortcut)) && "Mismatching io.KeyCtrl/io.KeyShift/io.KeyAlt/io.KeySuper vs io.KeyMods");
+    IM_ASSERT((key_mods == 0 || g.IO.KeyMods == key_mods) && "Mismatching io.KeyCtrl/io.KeyShift/io.KeyAlt/io.KeySuper vs io.KeyMods");
     IM_UNUSED(key_mods);
 
     // [EXPERIMENTAL] Recover from errors: You may call this yourself before EndFrame().