Make the PDFDataRangeTransport streaming unit-tests faster

[Snuffleupagus]

The delay between chunks when testing streaming is necessary to avoid the entire PDF document arriving all at once, since that would render those unit-tests somewhat pointless.
However, the delay is unnecessarily large which causes these unit-tests to be slower than necessary.

Also, update the range unit-tests to check the expected number of fetches exactly since those values are not supposed to vary.

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Note: This reduces the runtime of the should fetch document info and page using only streaming unit-test by 1200 ms.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.99%. Comparing base (e86e9d9) to head (1592124).

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #21238      +/-   ##
==========================================
+ Coverage   54.57%   55.99%   +1.42%     
==========================================
  Files         216      220       +4     
  Lines       58860    58964     +104     
==========================================
+ Hits        32120    33016     +896     
+ Misses      26740    25948     -792     

Flag	Coverage Δ
unittest	55.32% <ø> (?)
unittestcli	54.57% <ø> (ø)

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[timvandermeij]

Nice find; thank you for speeding up the tests!