Remove abort from FcCompareSize.

There doesn't appear to be a good reason to abort when 'v1' has type
FcTypeRange. If there does turn out to be a good reason for this then it
should be better documented and the code for handling this case removed.
At worst it seems -1 should be returned as it is for other unknown
types. It is possible this is left over debug code from the initial
implementation.
10 jobs for master in 6 minutes and 36 seconds
Status Job ID Name Coverage
  Build
passed meson macos #6020960
gst-macos-10.15

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passed meson-mingw-w64-build #6020957

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manual meson msys2 #6020961
docker windows 1809 allowed to fail manual
passed meson-shared-build #6020955

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passed meson-static-build #6020956

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passed meson vs2017 amd64 #6020958
docker windows 1809

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passed meson vs2017 x86 #6020959
docker windows 1809

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passed mingw-build #6020954

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passed shared-build #6020952

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passed static-build #6020953

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