RFR: 8340229: Improve opening sentence of FileInputStream constructor specification

[Brian Burkhalter]

Improve the first sentences of the three `FileInputStream` constructors, in particular removing the term "connection."

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Commit messages:
 - 8340229: Improve opening sentence of FileInputStream constructor specification

Changes: https://git.openjdk.org/jdk/pull/21223/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21223&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8340229
  Stats: 11 lines in 1 file changed: 0 ins; 4 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/21223.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21223/head:pull/21223

PR: https://git.openjdk.org/jdk/pull/21223