Removed `stable` option.

This is not necessary since ordering in INFO should not matter, also
this option is not available in Octave 5.x.

src/@dseries/projection.m

@@ -31,7 +31,7 @@ function o = projection(o, info, periods)  % --*-- Unitary tests --*--
 % [4] This projection routine only deals with exponential trends.
 
 % Fetch useful lines in info
-[~, ~, i2] = intersect(o.name, info(:,1), 'stable');
+[~, ~, i2] = intersect(o.name, info(:,1));
 INFO = info(i2,:);
 
 % Change number of periods in dseries object o