Check data file for contrib/opendap

[gassmoeller]

In #3552 we had to remove one data column from the input files in contrib/opendap/input_files to keep the example model working. The adiabatic boundary plugin now expects exactly one column for the lithosphere thickness, but the data file has two. However the model did not document which column it used and it is unclear which one was used in the past. We need confirmation from @kneumiller or @njinju or @dsarahstamps on which column to actually use as the lithosphere thickness.