booleanOverlap incorrectly returns true for adjoining polygons

[stevage]

v 6.5.0

This may be the same bug report as #2271 (it's unclear what the intention of that report is).

But, the definition of booleanOverlap is:

returns true if their intersection set results in a geometry different from both but of the same dimension

Two polygons that share an edge (only) have an intersection set which is a line, and hence of a different dimension (1 vs 2).

But actually booleanOverlap returns true, which then makes intersect throw an error.