Improve Triangles testing

[TheKrol]

In the description for a triangle, a valid triangle is only valid if def isosceles(sides):
a + b ≥ c
b + c ≥ a
a + c ≥ b
But you can pass the test without an equal sign. So for example a valid triangle that might fail without the equals is [2,2,4] of the isosceles function, or [1,3,4] for the scalene function.

[github-actions]

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