Answer
See below.
Work Step by Step
First, Mercury is small enough that it just appears as a dot crossing the disk of the sun, so measuring whether or not sunlight was bent is too difficult an experiment to carry out. There is too much background glare.
Second, that discussion doesn't even matter because the mass of Mercury is far too small to observe the effect even under ideal conditions. Light doesn't appreciably bend when it passes by Mercury.
This is discussed on page 690.