[jdk17] RFR: 8271489: (doc) Clarify Filter Factory example

[Roger Riggs]

Improve the clarity of comments in the ObjectInputFilter FilterInThread example.

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Commit messages:
 - 8271489: (doc) Clarify Filter Factory example
 - 8270398: Enhance canonicalization
 - 8270404: Better canonicalization
 - Merge
 - Merge
 - 8263531: Remove unused buffer int
 - 8262731: [macOS] Exception from "Printable.print" is swallowed during "PrinterJob.print"
 - 8269763: The JEditorPane is blank after JDK-8265167
 - 8265580: Enhanced style for RTF kit
 - 8265574: Improve handling of sheets
 - ... and 15 more: https://git.openjdk.java.net/jdk17/compare/c1304519...650e1561

Changes: https://git.openjdk.java.net/jdk17/pull/292/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17&pr=292&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8271489
  Stats: 1001 lines in 42 files changed: 625 ins; 181 del; 195 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/292.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/292/head:pull/292

PR: https://git.openjdk.java.net/jdk17/pull/292