Remove animation from loading spinner without spin

[hoxbro]

Fixes #6321

Animation is set on: :host(.loader.spin) div::after {

import panel as pn

pn.extension()
active = pn.indicators.LoadingSpinner(
    width=100, height=100, bgcolor="dark", value=True, color="primary"
)
idle = pn.indicators.LoadingSpinner(
    width=100, height=100, bgcolor="dark", value=False, color="primary"
)
pn.Row(active, idle).servable()

screenrecord-2024-02-08_12.51.44.mp4

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1e8e6af) 71.67% compared to head (30a17e9) 82.64%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #6324       +/-   ##
===========================================
+ Coverage   71.67%   82.64%   +10.97%     
===========================================
  Files         305      305               
  Lines       45445    45445               
===========================================
+ Hits        32572    37558     +4986     
+ Misses      12873     7887     -4986     

Flag	Coverage Δ
ui-tests	38.57% <ø> (?)
unitexamples-tests	71.66% <ø> (-0.01%)	⬇️

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