Webdoc: fix Fitting GISAS in 2D page

#523 (closed):

• https://bornagainproject.org/git-main/py/fitting/gisas-fit2d/

Faked experimenta data <-- typo

Faked experimental data have been generated by the script devtools/fakeData/fake-gisas1.py. <-- broken link

The faked data can be found at Examples/fit/data/faked-gisas1.txt.gz. <-- broken link