chore: enable dupword linter and remove duplicated words

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This MR enables dupword linter in golangci-lint config and fixes the following lint issues:

$ golangci-lint run
freeze_periods.go:70:1: Duplicate words (project) found (dupword)
issues.go:285:2: Duplicate words (the) found (dupword)
runners_test.go:354:12: Duplicate words (returned) found (dupword)
runners_test.go:376:12: Duplicate words (returned) found (dupword)
runners_test.go:398:12: Duplicate words (returned) found (dupword)
runners_test.go:430:12: Duplicate words (returned) found (dupword)
runners_test.go:462:12: Duplicate words (returned) found (dupword)
runners_test.go:494:12: Duplicate words (returned) found (dupword)
runners_test.go:526:12: Duplicate words (returned) found (dupword)
9 issues:
* dupword: 9