Replace the benchmark chart with SVG

Signed-off-by: Michał Górny <mgorny@quansight.com>

Author: mgorny

peps/pep-0817.rst

@@ -95,7 +95,7 @@ As illustrated by `archspec <https://github.com/archspec/archspec>`_,
 the ability to optimize a package for a specific architecture can lead to
 significant performance improvement.
 
-    .. figure:: pep-0817/avx512_gromacs_benchmark.png
+    .. figure:: pep-0817/avx512_gromacs_benchmark.svg
         :alt: A bar graph comparing GROMACS performance (in ns/day) with
               various targets. The first two bars are labeled "yum (2018.8)"
               and "generic (SSE2)", reach about 1.0 ns/day and are both