Arm backend: add new cmake line to vgf tutorial (#14935)

Missed updating docs in #14885

Signed-off-by: Erik Lundell <[email protected]>
(cherry picked from commit 29b98c3)

Author: Erik-Lundell

docs/source/tutorial-arm-vgf.md

@@ -171,6 +171,7 @@ cmake \
   -DCMAKE_BUILD_TYPE=Debug \
   -DEXECUTORCH_BUILD_EXTENSION_DATA_LOADER=ON \
   -DEXECUTORCH_BUILD_EXTENSION_MODULE=ON \
+  -DEXECUTORCH_BUILD_EXTENSION_NAMED_DATA_MAP=ON \
   -DEXECUTORCH_BUILD_EXTENSION_FLAT_TENSOR=ON \
   -DEXECUTORCH_BUILD_EXTENSION_TENSOR=ON \
   -DEXECUTORCH_BUILD_KERNELS_QUANTIZED=ON \