Correct location of previous versions

Author: wgropp

docs.md

@@ -16,6 +16,7 @@ MPI-5.0 was approved by the MPI Forum on June 5, 2025.
 *   [BibTeX file for citing MPI 5.0](mpi-5.0/citation.bib)
 *   [Unofficial HTML version of MPI 5.0](mpi-5.0/mpi50-report/mpi50-report.htm)
 
+## Previous Versions of the MPI Standard
 
 ## MPI 4.1
 
@@ -42,8 +43,6 @@ associated with an MPI operation, or inquiry procedures providing information
 about an operation, was produced and is available (see below for
 "Summary of the Semantics of all Operation-Related MPI Procedures")
 
-## Previous Versions of the MPI Standard
-
 ## MPI-3.1
 
 |<a href="images/mpi-report-3.1-2015-06-04-as-1book.jpg"><img alt="MPI-3.0 - Click to enlarge" src="images/mpi-report-3.1-2015-06-04-as-1book-thumb.jpg" width="90" /></a>|MPI-3.1 was approved by the MPI Forum on June 4, 2015.|