The wording of the Spanish original is:
Dijo: “Ese pretexto no se lo traga ni la mujer de Jonás”.
In Spanish, there is a colloquial figurative use of the verb tragar, that is, "to swallow", defined in this way in the DLE dictionary of the Real Academia Española:
Dar fácilmente crédito a las cosas, aunque sean inverosímiles. U. t. c. prnl. Le contó una mentira y no se la tragó.
That is, tragar in this sense means "easily believe things, even if they are unlikely". The dictionary gives us un example of usage of this verb which is similar to the one written by García Márquez: "le contó una mentira y no se la tragó", which means "he/she told him/her a lie, but he/she didn't believe it". This sense of "tragar" is quite usual in infomal speech in Spanish. The sentence in the novel means "not even Jonah's wife would believe that pretext".
That said, García Márquez has used in other writings the figure of Jonah's wife, where Jonah is indeed the biblical character, in reference to someone who easily believes any implausible story. The idea is that she would have believed the fact that Jonah spent three days in the belly of a fish and then was vomited out, something which seems incredible.
In this article by García Márquez published in El País newspaper, he says:
La literatura de ficción la inventó Jonás cuando convenció a su mujer de que había vuelto a casa con tres días de retraso porque se lo había tragado una ballena
which can be translated as
Fiction literature was invented by Jonah when he convinced his wife that he had returned home three days late because he had been swallowed by a whale.
Another example of a similar usage of the figure of Jonah's wife in García Márquez works has been pointed out by @GarethRees. It comes from One Hundred Years of Solitude:
[...] acostumbrado a vivir de las mujeres, y convencido de que se había casado con la esposa de Jonás, que se quedó tan tranquila con el cuento de la ballena
[...] used to live from women, and convinced that he had married Jonah's wife, who was was so content with the story of the whale.