Updating ScanPDF Date Format

[phutelmyer]

Describe the change
Prior to this change, the format for date strings in the PDF scanner would display as a timestamp with timezone information (ex: 2022-08-03 08:00:30-05:00). This is accurate, but is not standard with most other scanner date times.

This change converts the date string to ISO 8601 (ex: 2022-08-03T13:00:30Z)

Describe testing procedures
Updated test_scan_pdf.py tests, confirmed a passing test.

...
#21 92.78 tests/test_scan_pcap.py ..
#21 93.81 tests/test_scan_pdf.py .
#21 93.87 tests/test_scan_pe.py .
...

Sample output

{
        "elapsed": 0.0142052,
        "flags": [],
        "images": 1,
        "lines": 34,
        "links": [],
        "words": 418,
        "author": "Ryan.OHoro",
        "creator": "Microsoft® Word 2016",
        "creation_date": "2022-12-16T19:48:52Z",
        "dirty": False,
        "embedded_files": {"count": 0, "names": []},
        "encrypted": False,
        "needs_pass": False,
        "format": "PDF 1.5",
        "keywords": "",
        "language": "en",
        "modify_date": "2022-12-16T19:48:52Z",
        "old_xrefs": True,
        "pages": 1,
        "producer": "Microsoft® Word 2016",
        "repaired": False,
        "subject": "",
        "title": "",
        "xrefs": 40,
        "phones": [],
        "objects": {},
    }

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of and tested my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings