Change potentially misleading placeholder in "Finding your path"

[bld010]

twilioquest-dev-fundamentals/levels/tower_of_knowledge/objectives/fs-01-path/objective.json

Line 8 in c9b6d48

"placeholder": "/path/to/a/file.txt",

The correct answer in the "Finding your path" mission doesn't start with a /, so the placeholder could mislead players. I propose changing the placeholder to "path/to/a/file.txt"