Add back missing call to resize

[jfly]

The call to resize is pretty important... without it, nothing shows up
on the screen when I run flameshot (presumably because it's 0 pixels by
0 pixels large). This was accidentally removed when resolving merge
conflicts in 77c509e.

While I was in here, I also opted to delete some comments. I personally
am never a fan of commenting out code: if we need something, that's what
Git is for! And, just in case GitHub disappears, I thought it would be
nice to record my research in a Git commit about why I think removing
Qt::BypassWindowManagerHint is ok. Comments copied from
#731):

I played around with it [removing Qt::BypassWindowManagerHint] a bit
and it has some really nice properties for me as a Xmonad X11 user:

• It resolves Window focus gets lost after flameshot exits #784
• It also makes it possible for me to clearly see when flameshot has
  focus, and give it focus, which I'd argue is a workaround/fix for
  Esc does not close flameshot gui #1072, and also has
  some nice properties as @filipkilibarda mentioned: "Allows the user to
  switch workspaces while in the screenshot GUI..."

I did some git spelunking and here's the history of the current code:

• c4d9210 is the first commit where
  something like this showed up, but it used
  Qt::X11BypassWindowManagerHint, which is just an alias for
  Qt::BypassWindowManagerHint
• 0f30529 removed it (yay!)
• 11b0e2d added in
  Qt::BypassWindowManagerHint with somewhat cryptic message: "Capture
  window showing when mouse events are holded" message. I'm not sure what
  that means.
• Later, this commit a9b0c21 added a
  #ifdef Q_OS_WIN branch that made it so this
  Qt::BypassWindowManagerHint only happens on Linux, not Windows.

So, since flameshot doesn't currently target OSX, I think this change
only affects Linux. @borgmanJeremy if I did some investigation into how
this behaves with other window managers (and maybe wayland?) would you
be open to merging it up?
#731 (comment)
for more information.

Later, I investigated how things behave on Linux with a non-tiling
window manager:

I just installed xfce and tried this out, and as far as I can tell,
things work great! During a screenshot, I can alt-tab to other windows
and they end up on top of the ongoing screenshot, but I can click back
on the screenshot to continue editing the screenshot (strangely, I
cannot alt-tab back to the window). Keyboard shortcuts work as expected,
and this feels like an improvement in every way, IMO.