While Gifford was editor of the Quarterly Review, the source for this statement is an aside in an annotated edition of Ben Johnson's works, from 1816, not the Quarterly Review. Here is what Gifford wrote in his notes to The Alchemist:
According to him during the American Revolution a person of "that state" (i.e., New England) proposed to the Congress that English be suppressed and Hebrew raised in its stead.
H.L. Mencken famously called attention to this passage in his The American Language. He refers to the Marquis Francois Jean de Chastellux's book about his tour of America, from whence Gifford "seems to have picked up the story." Here is what Chastellux wrote, in the English translation of his book, Travels in North-America, in the years 1780, 1781, and 1782, printed in 1787:
"Some persons." No mention of Congress. As you cans see, these are slim reeds for this urban legend to rest on.
Here is a resolution passed by General Assembly of the state of Massachusetts-Bay in March of 1777: