chore: Update dev version to 3.0.dev0

[terriko]

The 3.0 release is planned for after Google Summer of Code winds down in September, this bump reflects that the current main branch will eventually become the 3.0 release.

[codecov-commenter]

Codecov Report

Merging #1319 (5435f80) into main (8e2cd7c) will decrease coverage by 2.15%.
The diff coverage is 17.18%.

@@            Coverage Diff             @@
##             main    #1319      +/-   ##
==========================================
- Coverage   81.26%   79.11%   -2.16%     
==========================================
  Files         270      271       +1     
  Lines        4826     4864      +38     
  Branches      575      585      +10     
==========================================
- Hits         3922     3848      -74     
- Misses        759      864     +105     
- Partials      145      152       +7     

Flag	Coverage Δ
longtests	79.11% <17.18%> (-2.16%)	⬇️

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

Impacted Files	Coverage Δ
cve_bin_tool/format_checkers.py	0.00% <0.00%> (ø)
test/test_cli.py	81.99% <25.00%> (-11.38%)	⬇️
cve_bin_tool/version.py	73.68% <50.00%> (+3.68%)	⬆️
cve_bin_tool/cvedb.py	82.42% <80.00%> (-0.61%)	⬇️
cve_bin_tool/cve_scanner.py	76.22% <100.00%> (-1.12%)	⬇️
cve_bin_tool/version_scanner.py	74.30% <100.00%> (-1.39%)	⬇️
cve_bin_tool/checkers/xml2.py	61.36% <0.00%> (-27.28%)	⬇️
test/test_json.py	68.96% <0.00%> (-20.69%)	⬇️
test/test_scanner.py	61.71% <0.00%> (-12.50%)	⬇️
... and 6 more

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