retain nomatch=FALSE for backwards compatibility

[mattdowle]

Resolves revdeps NADIA and VIM (highlighted in #5208) which use nomatch=FALSE. Were broken by #4353.

[codecov]

Codecov Report

Merging #5214 (9fdd0de) into master (a41ae4a) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 9fdd0de differs from pull request most recent head 0ef4c72. Consider uploading reports for the commit 0ef4c72 to get more accurate results

@@           Coverage Diff           @@
##           master    #5214   +/-   ##
=======================================
  Coverage   99.50%   99.50%           
=======================================
  Files          77       77           
  Lines       14531    14531           
=======================================
  Hits        14459    14459           
  Misses         72       72           

Impacted Files	Coverage Δ
R/data.table.R	99.89% <100.00%> (ø)

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