Update sphinxcontrib-mermaid requirement from <1 to <2

Updates the requirements on [sphinxcontrib-mermaid](https://github.com/mgaitan/sphinxcontrib-mermaid) to permit the latest version.
- [Changelog](https://github.com/mgaitan/sphinxcontrib-mermaid/blob/master/CHANGELOG.rst)
- [Commits](mgaitan/sphinxcontrib-mermaid@0.1...1.0.0)

---
updated-dependencies:
- dependency-name: sphinxcontrib-mermaid
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

pyproject.toml

@@ -138,7 +138,7 @@ docs = [
   "sphinx-autobuild==2021.3.14", # Newer versions stopped "watching" appropriately?
   "sphinx-copybutton",
   "sphinx-design-elements<1",
-  "sphinxcontrib-mermaid<1",
+  "sphinxcontrib-mermaid<2",
   "sphinxext-opengraph<1",
 ]
 dynamodb = [