Don't download UpdateVersionTable on Linux
Don't download UpdateVersionTable on Linux

On Linux we don't use the Sparkle mechanism to update the
application. Instead we rely on the system packaging mechanism.
We can save a few milliseconds on startup if we don't download
the version table.

BloomBooks/BloomDesktop,StephenMcConnel/BloomDesktop,gmartin7/myBloomFork,StephenMcConnel/BloomDesktop,gmartin7/myBloomFork,gmartin7/myBloomFork,StephenMcConnel/BloomDesktop,andrew-polk/BloomDesktop,BloomBooks/BloomDesktop,StephenMcConnel/BloomDesktop,JohnThomson/BloomDesktop,andrew-polk/BloomDesktop,andrew-polk/BloomDesktop,andrew-polk/BloomDesktop,BloomBooks/BloomDesktop,BloomBooks/BloomDesktop,StephenMcConnel/BloomDesktop,BloomBooks/BloomDesktop,gmartin7/myBloomFork,JohnThomson/BloomDesktop,andrew-polk/BloomDesktop,JohnThomson/BloomDesktop,gmartin7/myBloomFork,StephenMcConnel/BloomDesktop,gmartin7/myBloomFork,JohnThomson/BloomDesktop,JohnThomson/BloomDesktop,andrew-polk/BloomDesktop,BloomBooks/BloomDesktop