Fix prefixItems index reporting in ValidationError

[jhashkes]

• Fixed an issue when a prefixItems mismatch was identified, ValidationError was neglecting to report the instance index in json_path and the various deque paths
• Updated unit test

[codecov]

Codecov Report

Merging #862 (ff1a2bf) into main (2cf3dc2) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #862   +/-   ##
=======================================
  Coverage   98.29%   98.29%           
=======================================
  Files          19       19           
  Lines        3111     3111           
  Branches      377      377           
=======================================
  Hits         3058     3058           
  Misses         41       41           
  Partials       12       12           

Impacted Files	Coverage Δ
jsonschema/tests/test_validators.py	98.80% <ø> (ø)
jsonschema/_validators.py	98.44% <100.00%> (ø)

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[Julian]

Thanks!