The `VirtualSize` field was deprecated in [moby@1261fe6], and omitted / removed
in API v1.44 in [moby@913b0f5], and the corresponding formatting placeholder
was deprecated in [cli@f02301a].
This patch removes the formatting function, which also removes it from the
`docker image ls --format=json` output.
[moby@1261fe6]: 1261fe69a3
[moby@913b0f5]: 913b0f51ca
[cli@f02301a]: f02301ab5d
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
1b90a53be2