Remove libgconf install step on CI jobs

[louise-davies]

Description

Github changed the default machine from Ubuntu 22 to Ubuntu 24, which doesn't have libgconf-2-4. Equally, Cypress no longer needs this dependency so it can just be removed

Testing instructions

Add a set up instructions describing how the reviewer should test the code

• Review code
• Check Actions build
• Review changes to test coverage

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.39%. Comparing base (44b11eb) to head (a0585dc).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1692   +/-   ##
========================================
  Coverage    95.39%   95.39%           
========================================
  Files          183      183           
  Lines         7932     7932           
  Branches      2516     2510    -6     
========================================
  Hits          7567     7567           
  Misses         330      330           
  Partials        35       35           

Flag	Coverage Δ
common	94.27% <ø> (ø)
dataview	97.32% <ø> (ø)
download	96.03% <ø> (ø)
search	93.58% <ø> (ø)

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