Update plot images in plots e2e tests

[sharon-wang]

System details:

Positron and OS details:

The prerelease/2025.01 branch as of ce9358c and the main branch once #6007 is merged.

Interpreter details:

Any

Describe the issue:

From #5981 (comment):

The test failures appear to just be pixel shifts in the plots (maybe expected on this branch?)

Steps to reproduce the issue:

main branch test link: https://github.com/posit-dev/positron/actions/runs/12793422237?pr=6007

prerelease/2025.01 branch test link: https://github.com/posit-dev/positron/actions/runs/12777108705

Expected or desired behavior:

Plots tests should pass!

Were there any error messages in the UI, Output panel, or Developer Tools console?

Test output contains Image comparison failed with mismatch percentage...

    3 failed
      [e2e-electron] › areas/plots/plots.test.ts:42:7 › Plots › Python Plots › Python - Verifies basic plot functionality - Dynamic Plot [C608114] https://app.currents.dev/i/S5evItIhcu4wkkZh/test/659c9f63c8baa59c569c-083dbf10919e58e5a9f4 31.9s
      [e2e-electron] › areas/plots/plots.test.ts:82:7 › Plots › Python Plots › Python - Verifies basic plot functionality - Static Plot [C654401] https://app.currents.dev/i/S5evItIhcu4wkkZh/test/659c9f63c8baa59c569c-0e4cd2e6791b4e0b796e 22.5s
      [e2e-electron] › areas/plots/plots.test.ts:270:7 › Plots › R Plots › R - Verifies basic plot functionality [C628633] https://app.currents.dev/i/S5evItIhcu4wkkZh/test/659c9f63c8baa59c569c-e62389fadee8c548706a 15s