Remove duplicate line

In 231b7d670b, while copy-pasting some code into
ExecEvalJsonCoercionFinish(), I (amitlan) accidentally introduced
a duplicate line.  Remove it.

Reported-by: Jian He <jian.universality@gmail.com>
Discussion: https://postgr.es/m/CACJufxHcf=BpmRAJcjgfjOUfV76MwKnyz1x3ErXsWL26EAFmng@mail.gmail.com

src/backend/executor/execExprInterp.c

@@ -5228,7 +5228,6 @@ ExecEvalJsonCoercionFinish(ExprState *state, ExprEvalStep *op)
 		 * JsonBehavior expression.
 		 */
 		jsestate->escontext.error_occurred = false;
-		jsestate->escontext.error_occurred = false;
 		jsestate->escontext.details_wanted = true;
 	}
 }