changesetRevisions called common.FlagErrorf, which does not exist,
breaking the build. Use sheetsValidationForFlag so the errors carry the
offending flag param like the rest of the sheets validation paths.
Also reword two doc comments in lark_sheet_history_revert.go that used
'' for an empty shell string: gofmt (Go 1.19+) rewrites '' in doc
comments to a curly quote, leaving the file permanently unformatted.