Update help-service.ts

[meob]

Adding GATHER and GATHER MERGE node description

[pgiraud]

Thanks for your contribution. May I suggest to rephrase it a bit?

[pgiraud]

Here is what my colleagues proposed:

« Gather » reads the results of the parallel workers, in an undefined order.
« Gather Merge » reads the results of the parallel workers, preserving any ordering.

If you agree with these new statements, would you be kind to update your PR? Thanks.

[meob]

Here is what my colleagues proposed:

« Gather » reads the results of the parallel workers, in an undefined order.
« Gather Merge » reads the results of the parallel workers, preserving any ordering.

If you agree with these new statements, would you be kind to update your PR? Thanks.

Of course: better than mine... sorry for the delay I had to change my primary email