Update scripts/whitelist.sh

Bug fix

The escape sequence for GRID files was wrong (see changes)

Before bugfix

Find files that have been added in last commit...
ERROR: file: 999xxx/999999/mc_13TeV.sample.GRID.tar.gz not in white list

Tests

After bugfix

Find files that have been added in last commit...
OK: file: 999xxx/999999/mc_13TeV.sample.GRID.tar.gz in white list