Bump graphviz from 0.20.1 to 0.21 in /requirements (#2372)

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements/requirements_docs.txt

@@ -1,6 +1,6 @@
 ansys-sphinx-theme[autoapi]==1.4.4
 enum-tools[sphinx]==0.13.0
-graphviz==0.20.1
+graphviz==0.21
 imageio==2.37.0
 imageio-ffmpeg==0.6.0
 pypandoc==1.15

requirements/requirements_test.txt

@@ -1,6 +1,6 @@
 ansys-platform-instancemanagement==1.1.2
 coverage==7.8.2
-graphviz==0.20.1
+graphviz==0.21
 imageio==2.37.0
 imageio-ffmpeg==0.6.0
 pypandoc_binary==1.15