Apply some minor doc fixes

[dstrain115]

• quirk_url_to_circuit and quirk_json_to_circuit had weird HTML in them.
• concat_ragged had a bunch of pre tags in the output.

I believe these changes fix the markdown generation.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (f715527) 97.88% compared to head (cd85881) 97.88%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6289   +/-   ##
=======================================
  Coverage   97.88%   97.88%           
=======================================
  Files        1104     1104           
  Lines       95830    95841   +11     
=======================================
+ Hits        93805    93818   +13     
+ Misses       2025     2023    -2     

Files Changed	Coverage Δ
cirq-core/cirq/circuits/circuit.py	98.43% <ø> (ø)
cirq-core/cirq/devices/named_topologies.py	98.26% <ø> (ø)
cirq-core/cirq/interop/quirk/url_to_circuit.py	99.35% <ø> (ø)
cirq-core/cirq/protocols/apply_channel_protocol.py	100.00% <ø> (ø)
examples/two_qubit_gate_compilation.py	97.36% <ø> (-0.07%)	⬇️
cirq-core/cirq/contrib/svg/svg.py	99.14% <100.00%> (+<0.01%)	⬆️
...q-core/cirq/experiments/qubit_characterizations.py	99.63% <100.00%> (-0.01%)	⬇️
cirq-core/cirq/linalg/decompositions.py	96.52% <100.00%> (ø)
cirq-core/cirq/vis/heatmap.py	98.80% <100.00%> (+0.01%)	⬆️
cirq-core/cirq/vis/heatmap_test.py	98.05% <100.00%> (+0.04%)	⬆️
... and 4 more

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