Bump cairosvg from 2.4.2 to 2.5.1

Bumps [cairosvg](https://github.com/Kozea/CairoSVG) from 2.4.2 to 2.5.1.
- [Release notes](https://github.com/Kozea/CairoSVG/releases)
- [Changelog](https://github.com/Kozea/CairoSVG/blob/master/NEWS.rst)
- [Commits](Kozea/CairoSVG@2.4.2...2.5.1)

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -9,7 +9,7 @@ authlib==0.13             # via -r requirements.in
 blinker==1.4              # via flask-mail, sentry-sdk
 blurhash==1.1.4           # via mastodon.py
 cairocffi==1.1.0          # via cairosvg
-cairosvg==2.4.2           # via -r requirements.in
+cairosvg==2.5.1           # via -r requirements.in
 certifi==2020.4.5.1       # via -r requirements.in, requests, sentry-sdk
 cffi==1.14.0              # via cairocffi, cryptography
 chardet==3.0.4            # via requests