Replace of PyPDF2 package with pypdf

[douglatornell]

Resolve Jun-2023 security alert re: CVE-2023-36464 infinite loop vulnerability and deprecation of PyPDF2.

Also update test suite re:

• issue #121
• issue #81
• issue #82

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 93.61702% with 3 lines in your changes missing coverage. Please review.

Project coverage is 77.76%. Comparing base (506a986) to head (58bb239). Report is 33 commits behind head on main.

Files	Patch %	Lines
nowcast/workers/make_surface_current_tiles.py	40.00%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #263 +/- ## ========================================== - Coverage 77.77% 77.76% -0.01% ========================================== Files 133 133 Lines 18822 18816 -6 Branches 1914 1910 -4 ========================================== - Hits 14639 14633 -6 Misses 4116 4116 Partials 67 67 ``` | [Flag](https://app.codecov.io/gh/SalishSeaCast/SalishSeaNowcast/pull/263/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=SalishSeaCast) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/SalishSeaCast/SalishSeaNowcast/pull/263/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=SalishSeaCast) | `77.76% <93.61%> (-0.01%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=SalishSeaCast#carryforward-flags-in-the-pull-request-comment) to find out more.

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[douglatornell]

Tested successfully in production to manually reproduce 17may24 forecast tiles, and did 18may24 forecast2 tiles via automation.