Tweak indents to fix list numbering.

[pp-mo]

This should fix a problem with the 3.7.0rc0 docs that was pointed out : the numbering of the lists of items in the whatsnew section was messed up by the insertion of anchor points for the 'feature items' para.

I think this fixes that.
We will include it in the main release, and in any subsequent bugfixes, but we won't make a bugfix release for this alone.
So for now, I'll include it here and, when this is agreed, it will also go into the v3.7.x mergeback to main.

[pp-mo]

Ping @HGWright please see what you think of this.

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (75ff780) 89.37% compared to head (05a0e00) 89.37%.

Additional details and impacted files

@@           Coverage Diff           @@
##           v3.7.x    #5427   +/-   ##
=======================================
  Coverage   89.37%   89.37%           
=======================================
  Files          89       89           
  Lines       22443    22443           
  Branches     5381     5381           
=======================================
  Hits        20058    20058           
  Misses       1639     1639           
  Partials      746      746           

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[HGWright]

After checking out the RTD, the changes seem to have the desired effect so I'm happy to merge this.