Grid identifiers don't have to start at zero

[mcflugen]

I've removed some wording in the description of get_var_grid that said grid ids start at 0. In fact, they can be any integer at all.

[Copilot]

Pull Request Overview

Updates the documentation for get_var_grid by removing an outdated note that grid identifiers must start at 0, since they can be any integer.

• Removed the misleading implementation note about zero-based grid IDs.

Comments suppressed due to low confidence (1)

docs/source/bmi.var_funcs.md:57

• [nitpick] Consider adding a replacement note clarifying that grid identifiers can be any integer value, e.g., 'Grid identifiers can be any integer, not necessarily starting at 0.'

-- Grid identifiers start at 0.