When, exactly, were the DC-8’s airbrakes removed? The DC-8 was originally equipped with airbrakes on the lower rear fuselage, but these were quickly removed.  Wikipedia says that they were removed before the DC-8 entered service:

[...]  Douglas made a massive effort to close the gap with Boeing, using no fewer than ten aircraft for flight testing to achieve FAA certification for the first of the many DC-8 variants in August 1959.  Much needed to be done: the original air brakes on the lower rear fuselage were found ineffective and were deleted as engine thrust reversers had become available...

Emphasis added.
However, according to the CAB report on the crash of United Airlines Flight 859, the first few DC-8-10s, at least, did have airbrakes when they entered service, and at least one was using them as late as July 1961:

When this action failed to straighten the landing roll he knew the aircraft was going to leave the runway.  He said he used the emergency airbrakes to slow the airplane as much as possible before leaving the runway.  [...]
[...]  The second officer said that after touchdown a series of events occurred which he could not place in sequence with any degree of certainty.  He saw ejector indicator lights blinking, heard a foot thumper, saw the captain reach for the emergency airbrake handle, and saw that the aircraft was heading about 30 degrees off the runway.  [...]  [page 4 of the report]

Emphasis added.
And it’s definitely not misusing the term “airbrakes” to refer to the aircraft’s wing spoilers, since it refers to those as “spoilers” elsewhere in the report.
When were the DC-8’s fuselage airbrakes removed?
The DC-8 is equipped with emergency air brake system. This isn't the type of air brakes you might expect on an airplane, but rather on a truck. The captain could pull a handle on the instrument panel to release pressurized air into the hydraulic brake system in the event of hydraulic pressure loss, as explained in this AAIB bulletin. The fuselage air brakes were removed from the first prototype, no DC-8 entered service with them. Although the wing spoilers are not used as speed brakes in flight, reverse thrust is allowed on the inboard engines during descent.