docs: Fix a few typos

There are small typos in:
- PACKAGING.rst

Fixes:
- Should read `instructions` rather than `instuctions`.
- Should read `command` rather than `commad`.

Signed-off-by: Tim Gates <tim.gates@iress.com>

PACKAGING.rst

@@ -5,6 +5,6 @@ Make sure maintainer dependencies are installed::
 
     pip install -e .[maintainer,dev]
 
-Run release commad and follow prompt instuctions::
+Run release command and follow prompt instructions::
 
     fullrelease