[rasterio] Remove unused stubtest allowlist entry

`Geometry` now lives in the blanket-allowlisted `rasterio._typing` module
and is only re-exported from `rasterio.features`, so stubtest no longer
flags `rasterio.features.Geometry` and the allowlist entry was unused.

Author: thomas-maschler

stubs/rasterio/@tests/stubtest_allowlist.txt

@@ -3,7 +3,6 @@ rasterio\._typing
 rasterio\._affine_types
 
 # Stubs-only type aliases referenced in signatures only.
-rasterio\.features\.Geometry
 rasterio\.merge\.MethodFunction
 
 # Cython implementation-detail attributes auto-generated on every