Temporarily drop --disable-c++17 from Coverity builds

...to see whether the Coverity issue has solved itself by now (see
0f3b0ec9 "Avoid C++17 mode for Coverity Scan"
for details)

Change-Id: I1086d6b79217af51a84e347a0d13f323429b37d0

distro-configs/LibreOfficeCoverity.conf

---disable-c++17
 --enable-assert-always-abort
 --without-help
 --enable-gio