[IO-414] Don't write a BOM on every (or any) line

[elharo]

Per JDK docs, "When decoding, the UTF-16 charset interprets the byte-order mark at the beginning of the input stream to indicate the byte-order of the stream but defaults to big-endian if there is no byte-order mark; when encoding, it uses big-endian byte order and writes a big-endian byte-order mark."

[codecov-commenter]

Codecov Report

Merging #492 (25c4e69) into master (877b9e3) will increase coverage by 0.10%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #492      +/-   ##
============================================
+ Coverage     84.97%   85.07%   +0.10%     
- Complexity     3372     3373       +1     
============================================
  Files           227      227              
  Lines          8080     8082       +2     
  Branches        953      954       +1     
============================================
+ Hits           6866     6876      +10     
+ Misses          960      951       -9     
- Partials        254      255       +1     

Files	Coverage Δ
src/main/java/org/apache/commons/io/IOUtils.java	86.81% <100.00%> (+0.04%)	⬆️

... and 2 files with indirect coverage changes

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