Set proper plot scales for ancillary plots

[krzywon]

Description

This sets the default axis scales for plots based on their plot role. All plots are set to log/log in v6.0.0, including residuals, polydispersity, and P(r) plots. This also removes a matplotlib version check that should no longer be relevant.

Review Checklist:

Documentation (check at least one)

• There is nothing that needs documenting
• Documentation changes are in this PR
• There is an issue open for the documentation (link?)

Installers

• There is a chance this will affect the installers, if so
  • Windows installer (GH artifact) has been tested (installed and worked)
  • MacOSX installer (GH artifact) has been tested (installed and worked)

Licencing (untick if necessary)

• The introduced changes comply with SasView license (BSD 3-Clause)