qmlplugindump: Update help output
qmlplugindump: Update help output

We dropped the 4.7 import a while ago.

Change-Id: I8ae8d11b890374c3ec6e87556a7de1f064d37f38
Reviewed-by: Christian Kamm <afb711f88e55c3f2d1b57cdc8d937fab8e46ae57@incasoftware.de>

kobolabs/qtquick1,kobolabs/qtquick1,kobolabs/qtquick1,kobolabs/qtquick1,kobolabs/qtquick1,kobolabs/qtquick1