boards: mps3_an547: Fix strange symbol in example run command

Fix strange symbol instead of underscore in example run command

Signed-off-by: Joakim Andersson <joakim.andersson@nordicsemi.no>
diff --git a/boards/arm/mps3_an547/doc/index.rst b/boards/arm/mps3_an547/doc/index.rst
index df6568e..347b5af 100644
--- a/boards/arm/mps3_an547/doc/index.rst
+++ b/boards/arm/mps3_an547/doc/index.rst
@@ -222,7 +222,7 @@
 
 .. code-block:: bash
 
-   $ west build -b mps3_an547 samples/hello°world -DEMU_PLATFORM=qemu -t run
+   $ west build -b mps3_an547 samples/hello_world -DEMU_PLATFORM=qemu -t run
 
 
 Note, however, that the Ethos-U55 NPU is not available in QEMU. If you require