Fix VP1 crash when cleaning input paths
This MR fixes a crash happenning when VP1 tries to clean the input paths where it looks for plugins and libraries.
That comes from the use of the removeAll("string")
Qt5 method, which apparently has (and the Qt5 docs states that) unexpected behavior when used within a loop.
I replaced that with a more standard removeAt(idx)
method.
NOTE: we need this fix in 24.0 for P1 and for debugging DD. The MR is NOT output-changing, and no Athena packages depend on VP1, so it is safe to merge this in 24.0.