I read in Wiktionary:
This spelling of the word was officially abolished in 1956 in favor of чёрт and is no longer in use. Both variants are pronounced identically.
I see in Ngram Google Books that it was indeed common before 1956 to write чорт in books.
Wikipedia says that in Belorussian and Ukrainian, this word is still spelt as чорт.
The new spelling, чёрт, has a disadvantage: if the dots over е are omitted as usual, the word becomes indistinguishable in writing from the plural genitive of the Russian word черта (line, trait, feature).
What was the motivation to officially abolish the spelling чорт in favor of чёрт in 1956? Could it be that someone superstitious wanted to save Russians from explicitly referring to devils and thought that replacing o by ё/e would do the trick to keep black powers at bay?