Remove TranscodingStreams dependency

[nhz2]

I'm not sure why TranscodingStreams is a dependency of this package.

Both uses in:

https://github.com/JuliaIO/ProtoBuf.jl/blob/3eb59e1cf4e9bb014fbdea201b40fe265cee79d4/src/codec/vbyte.jl#L2-L4

and

https://github.com/JuliaIO/ProtoBuf.jl/blob/3eb59e1cf4e9bb014fbdea201b40fe265cee79d4/src/lexing/Lexers.jl#L48

are relying on internal details of TranscodingStreams that may break in the future at any time.

Ref: https://github.com/JuliaLang/julia/pull/49125

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.99%. Comparing base (3eb59e1) to head (bcc6c0b).

Files	Patch %	Lines
src/codec/vbyte.jl	0.00%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #253      +/-   ##
==========================================
+ Coverage   92.96%   92.99%   +0.03%     
==========================================
  Files          25       25              
  Lines        2813     2812       -1     
==========================================
  Hits         2615     2615              
+ Misses        198      197       -1     

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[nhz2]

This seems to be indirectly causing some issues. Ref: https://github.com/JuliaIO/TranscodingStreams.jl/issues/234