Remove TranscodingStreams dependency

[nhz2]

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

Both uses in:

ProtoBuf.jl/src/codec/vbyte.jl

Lines 2 to 4 in 3eb59e1

	@inline function _unsafe_write(io::S, ref::Ref{T}, nb::Integer) where {T,S<:Union{TranscodingStream,BufferedOutputStream,BufferedInputStream}}
	GC.@preserve ref unsafe_write(io, Base.unsafe_convert(Ref{T}, ref)::Ptr, nb)
	end

and

ProtoBuf.jl/src/lexing/Lexers.jl

Line 48 in 3eb59e1

filepath(io::TranscodingStreams.TranscodingStream) = filepath(io.stream)

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

Ref: JuliaLang/julia#49125

[codecov]

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 ⚠️

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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[quinnj]

I think this is a good cleanup; @Drvi, do you know if there's a specific use-case where we need the TranscodingStream where we can't just rely on something more abstract/generic?

[nhz2]

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