Spurious warning with single spatial filter in 0.3.x

https://github.com/ansys/pyedb-core/blob/dab8644d164055a8ed7356c0fd111edd4f4e5010/src/ansys/edb/core/layout_instance/layout_instance.py#L161-L168

This block, still on `v0.3.3`, issues a warning even when only one spatial filter is present resulting in spurious warnings. `main` appears to remove the workaround as at some point the gRPC server fix is in place but if that cannot be backported to 0.3.x we should clean up this warning.

Start in src/ansys/edb/core/layout_instance/layout_instance.py at lines 161-168 and inspect how the single spatial filter is handled in v0.3.3. Compare the corresponding code on main, then verify that one spatial filter no longer produces a warning while the intended workaround remains covered for multiple filters.

Written by the indexing model from the issue text.