chore: Install pandoc manually from GitHub release binaries

[matthewfeickert]

Description

• Ubuntu 22.04 (current operating system for GitHub Actions runners for 'ubuntu-latest') will install pandoc v2.9.2.1 through apt-get which is too old for modern versions of nbsphinx. Installing directly from binaries provided on GitHub allows a workaround for getting newer versions of pandoc on runners until the GitHub Actions runner environment updates.
  • Avoids

RuntimeWarning: You are using an unsupported version of pandoc (2.9.2.1).
Your version must be at least (2.14.2) but less than (4.0.0).

from nbsphinx.

Checklist Before Requesting Reviewer

• Tests are passing
• "WIP" removed from the title of the pull request
• Selected an Assignee for the PR to be responsible for the log summary

Before Merging

For the PR Assignees:

• Summarize commit messages into a comprehensive review of the PR

* Ubuntu 22.04 (current operating system for GitHub Actions runners for
  'ubuntu-latest') will install pandoc v2.9.2.1 through apt-get which is
  too old for modern versions of nbsphinx. Installing directly from
  binaries provided on GitHub allows a workaround for getting newer versions
  of pandoc on runners until the GitHub Actions runner environment
  updates.
   - Avoids

---
RuntimeWarning: You are using an unsupported version of pandoc (2.9.2.1).
Your version must be at least (2.14.2) but less than (4.0.0).
---

   from nbsphinx.

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (2325b05) 98.30% compared to head (266c254) 98.30%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2307   +/-   ##
=======================================
  Coverage   98.30%   98.30%           
=======================================
  Files          69       69           
  Lines        4535     4535           
  Branches      802      802           
=======================================
  Hits         4458     4458           
  Misses         45       45           
  Partials       32       32           

Flag	Coverage Δ
contrib	97.88% <ø> (ø)
doctest	61.05% <ø> (ø)
unittests-3.10	96.31% <ø> (ø)
unittests-3.11	96.31% <ø> (ø)
unittests-3.8	96.33% <ø> (ø)
unittests-3.9	96.36% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[matthewfeickert]

The runtime warning doesn't kill the build, so while this isn't stricly necessary the Ubuntu version of pandoc is very old, and so maybe it is better to use something outside the package manager but more to date.