Fix KGlobalAccel build with Qt 5.13 prerelease.
Using the upcoming Qt 5.13 prerelease causes kglobalaccel to fail to
build the moc for component.cpp. Oddly, other frameworks in KF5
The essence of the issue is that you shouldn't #include "foo.moc" from
within a C++ namespace. With earlier Qt this would have worked since
only symbols relevant to the current C++ namespace were defined.
But now, the moc generates files that rely on parts of the
C++ standard library being available, and duly includes a line #include
<memory>. At the top namespace level this works great. Including
<memory> from within our own namespace works less well, producing error
messages that cause LLVM to give up early.
Fixed by just removing the entry since CMake is automoc'ing anyways.
Differential Revision: https://phabricator.kde.org/D17647