Make FontInfo::scan return a std::vector object

... rather than a pointer to a std::vector.  Given that a
std::vector is little more than a pointer and some size
information, there is no need to create std::vector objects
on the heap.  Returning them by value is just as fast
(the vector content is not copied), and makes the code
more readable, too.
6 jobs for modernize-fontinfo in 13 minutes and 3 seconds (queued for 19 seconds)
Status Job ID Name Coverage
  Build
passed #784218
build

00:03:06

passed #784223
build_android

00:02:03

passed #784219
build_clang_libcpp

00:09:38

passed #784222
build_clazy

00:04:02

passed #784221
build_mingw64_fedora

00:03:24

passed #784220
build_ubuntu_16_04

00:02:25