Update README to fix Bolt link

[ionred]

Fix bolt link - Directory changed on puppet's website.

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Please take some time to answer the following questions as best you can:

• Why is it awesome?
  n/a, link fix

• Have you used it? For how long?
  n/a, link fix

• Is this in a personal or professional setup?
  n/a, link fix

• How many devices/users/services/... do you manage with it?
  n/a, link fix

• Biggest pros/cons compared to other solutions?
  n/a, link fix

• Any other comments about your use case, things you've found excellent, limitations you've encountered... ?