CI is failing on the latest Julia master

[DilumAluthge]

Looks like the Base.write_sub function is no longer available on the latest Julia master?

See e.g. https://github.com/JuliaText/TextAnalysis.jl/pull/251/checks?check_run_id=2242561742 (triggered by #251):

Summarizer: Error During Test at /home/runner/work/TextAnalysis.jl/TextAnalysis.jl/test/summarizer.jl:1
  Got exception outside of a @test
  UndefVarError: write_sub not defined
  Stacktrace:
    [1] remove_patterns(s::SubString{String}, rex::Regex)
      @ TextAnalysis ~/work/TextAnalysis.jl/TextAnalysis.jl/src/preprocessing.jl:486
    [2] remove_patterns!
      @ ~/work/TextAnalysis.jl/TextAnalysis.jl/src/preprocessing.jl:508 [inlined]
    [3] remove_patterns!(crps::Corpus{StringDocument{SubString{String}}}, rex::Regex)
      @ TextAnalysis ~/work/TextAnalysis.jl/TextAnalysis.jl/src/preprocessing.jl:534
    [4] prepare!(crps::Corpus{StringDocument{SubString{String}}}, flags::UInt32; skip_patterns::Set{AbstractString}, skip_words::Set{AbstractString})
      @ TextAnalysis ~/work/TextAnalysis.jl/TextAnalysis.jl/src/preprocessing.jl:415
    [5] prepare!
      @ ~/work/TextAnalysis.jl/TextAnalysis.jl/src/preprocessing.jl:406 [inlined]
    [6] summarize(d::StringDocument{String}; ns::Int64)
      @ TextAnalysis ~/work/TextAnalysis.jl/TextAnalysis.jl/src/summarizer.jl:22
    [7] summarize(d::StringDocument{String})
      @ TextAnalysis ~/work/TextAnalysis.jl/TextAnalysis.jl/src/summarizer.jl:18
    [8] macro expansion
      @ ~/work/TextAnalysis.jl/TextAnalysis.jl/test/summarizer.jl:16 [inlined]
    [9] macro expansion
      @ /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.7/Test/src/Test.jl:1153 [inlined]
   [10] top-level scope
      @ ~/work/TextAnalysis.jl/TextAnalysis.jl/test/summarizer.jl:2
   [11] include(fname::String)
      @ Base.MainInclude ./client.jl:451
   [12] top-level scope
      @ ~/work/TextAnalysis.jl/TextAnalysis.jl/test/runtests.jl:22
Test Summary: | Error  Total
Summarizer    |     1      1