Delete long-term deprecated code

[magicDGS]

Description

Closes https://github.com/samtools/htsjdk/issues/955 Closes https://github.com/samtools/htsjdk/issues/972

Checklist

• [x] Code compiles correctly
• [ ] New tests covering changes and new functionality
• [x] All tests passing
• [x] Extended the README / documentation, if necessary
• [x] Is not backward compatible (breaks binary or source compatibility)

[codecov-io]

Codecov Report

Merging #1213 into master will increase coverage by 0.137%. The diff coverage is n/a.

@@               Coverage Diff               @@
##              master     #1213       +/-   ##
===============================================
+ Coverage     68.702%   68.839%   +0.137%     
+ Complexity      8061      8059        -2     
===============================================
  Files            542       540        -2     
  Lines          32711     32640       -71     
  Branches        5533      5523       -10     
===============================================
- Hits           22473     22469        -4     
+ Misses          8038      7969       -69     
- Partials        2200      2202        +2

Impacted Files	Coverage Δ	Complexity Δ
...samtools/util/AsyncBlockCompressedInputStream.java	72% <0%> (-4%)	12% <0%> (-1%)
...va/htsjdk/samtools/sra/SRAIndexedSequenceFile.java	62.162% <0%> (-2.703%)	6% <0%> (-1%)