Update SBF docs, fixes #4528

[kellen]

Updates ScalableBloomFilter docs to more completely and correctly describe its behavior.

See this gist for code to estimate false positive probability, capacity, and size: https://gist.github.com/kellen/38f47f84bd02c7d64d678add5d8b79f2

[codecov]

Codecov Report

Merging #4693 (8fda0ed) into main (470c80f) will not change coverage.
The diff coverage is n/a.

❗ Current head 8fda0ed differs from pull request most recent head edea798. Consider uploading reports for the commit edea798 to get more accurate results

@@           Coverage Diff           @@
##             main    #4693   +/-   ##
=======================================
  Coverage   60.64%   60.64%           
=======================================
  Files         286      286           
  Lines       10453    10453           
  Branches      694      694           
=======================================
  Hits         6339     6339           
  Misses       4114     4114           

Impacted Files	Coverage Δ
...src/main/scala/com/spotify/scio/coders/Coder.scala	85.39% <ø> (ø)
...spotify/scio/hash/MutableScalableBloomFilter.scala	95.58% <ø> (ø)

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