doc: fix link in flux-shell(1) cpu-affinity documentation

Problem: The documentation of the cpu-affinity shell option in the
flux-shell(1) manpage references the `hwloc_cpuset_t(3)` manpage,
but the link does not exist.

Reference the `hwlocality_bitmap(3)` manpage instead, and use a
direct link to the hwloc docs v2.9.0 since hwlocality_bitmap(3)
doesn't exist on the default manpage site (linux.die.net).

Update the spelling dictionary.

doc/man1/flux-shell.rst

@@ -267,7 +267,9 @@ options are supported by the builtin plugins of ``flux-shell``:
   If *OPT* starts with ``map:``, then the rest of the option is taken
   as a semicolon-delimited list of cpus to allocate to each task. Each
   entry in the list can be in one of the :linux:man7:`hwloc` list,
-  bitmask, or taskset formats (See :linux:man3:`hwloc_cpuset_t`).
+  bitmask, or taskset formats (See
+  `hwlocality_bitmap(3) <https://www.open-mpi.org/projects/hwloc/doc/v2.9.0/a00181.php>`_,
+  especially the ``hwloc_bitmap_*_sscanf()`` functions).
   The default is ``on``, which binds all tasks to the assigned set
   of cores in the job.
 

doc/test/spell.en.pws

@@ -711,3 +711,5 @@ noverify
 sdbus
 sdexec
 NONINTERACTIVE
+hwlocality
+sscanf