UndefVarError: write_sub not defined. Cannot access internal Base API

Elly tries to access the internal Base method Base.write_sub in rpc.jl:861

This leads to an UndefVarError in julia 1.7.2:
```
ERROR: UndefVarError: write_sub not defined
Stacktrace:
[1] getproperty
@ ./Base.jl:35 [inlined]
[2] write(writer::Elly.HDFSBlockWriter, buff::Vector{UInt8})
@ Elly ~/.julia/packages/Elly/Ia03N/src/rpc.jl:861
[3] _write(writer::Elly.HDFSFileWriter, data::Vector{UInt8})
@ Elly ~/.julia/packages/Elly/Ia03N/src/api_hdfs_io.jl:298
[4] write
@ ~/.julia/packages/Elly/Ia03N/src/api_hdfs_io.jl:309 [inlined]
[5] cp(frompath::String, topath::Elly.HDFSFile; offset::UInt64, len::UInt64, crc::Bool)
@ Elly ~/.julia/packages/Elly/Ia03N/src/api_hdfs_io.jl:385
[6] cp
@ ~/.julia/packages/Elly/Ia03N/src/api_hdfs_io.jl:365 [inlined]
```
It still works in julia 1.6