Fix typo in policy help documentation
The field is called ignoreDotFiles in JSON, but the documentation says
dotIgnoreFiles. Fix the docs to refer to the correct field name.
const policyEditFilesHelpText = `
# Which files to include in snapshots. Options include:
# "ignore": ["*.ext", "*.ext2"]
- # "dotIgnoreFiles": [".gitignore", ".kopiaignore"]
+ # "ignoreDotFiles": [".gitignore", ".kopiaignore"]
# "maxFileSize": number
# "noParentDotFiles": true
# "noParentIgnore": true
