Increase level of MPI subsection headers

Author: carterbox

src/maintainer/knowledge_base.rst

@@ -488,7 +488,7 @@ and apply the appropriate conditionals in your build:
 
 
 Preferring a provider (usually nompi)
-"""""""""""""""""""""""""""""""""""""
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 Up to here, mpi providers have no explicit preference. When choosing an MPI provider, the mutual exclusivity of
 the ``mpi`` metapackage allows picking between mpi providers by installing an mpi provider, e.g.
@@ -580,7 +580,7 @@ Remove the ``if mpi...`` condition if all variants should create a strict runtim
 chosen at build time (i.e. if the nompi build cannot be run against the mpich build).
 
 Complete example
-""""""""""""""""
+^^^^^^^^^^^^^^^^
 
 Combining all of the above, here is a complete recipe, with:
 
@@ -660,7 +660,7 @@ mpi-metapackage exclusivity allows ``mpi_*`` to resolve the same as ``mpi_{{ mpi
 if ``{{ mpi }}`` is also a direct dependency, though it's probably nicer to be explicit.
 
 Just mpi example
-""""""""""""""""
+^^^^^^^^^^^^^^^^
 
 Without a preferred ``nompi`` variant, recipes that require mpi are much simpler. This is all that is needed: