Fix docstring markup in sage/plot and sage/graphs

[kwankyu]

Part of #34157:

sage/plot/polygon.py:99:1: RST215 Inline interpreted text or phrase reference start-string without end-string.
sage/plot/polygon.py:113:1: RST215 Inline interpreted text or phrase reference start-string without end-string.
sage/graphs/dot2tex_utils.py:89:1: RST201 Block quote ends without a blank line; unexpected unindent.
sage/graphs/dot2tex_utils.py:91:1: RST301 Unexpected indentation.
sage/graphs/graph_plot.py:50:1: RST299 The "csv-table" directive requires content; none supplied.

Component: documentation

Author: Frédéric Chapoton

Branch/Commit: c088449

Reviewer: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/34164

[fchapoton]

Branch: u/chapoton/34164

[fchapoton]

Commit: c088449

[fchapoton]

comment:2

done and checked

there remains a failure in graphs, about csv directive lacking content. This is not a true error, as we dynamically fill the content. This need to be excluded from the checks somehow.

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New commits:

c088449

rst fixes in plot and graphs

[fchapoton]

Author: Frédéric Chapoton

[mkoeppe]

Reviewer: Matthias Koeppe

[vbraun]

Changed branch from u/chapoton/34164 to c088449