OPENNLP-1512 Fix incorrect encoding used in Conll02NameSampleStream

[mawiesne]

Notes

Verification conducted via a local SNAPSHOT distr build of the OpenNLP CLI tooling and the example in the OpenNLP doc, see: https://opennlp.apache.org/docs/2.3.0/manual/opennlp.html#tools.corpora.conll.2002

With this PR, the input esp.train is now read 'as is' (ISO_8859_1), with the resulting corpus txt file written correctly, that is, UTF-8. Result: No Spanish accents are corrupted or missing.

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[mawiesne]

Side note: The issue (OPENNLP-1512) was discovered while investigating OPENNLP-1190.