ORC: Fix additional typos in ORCSchemaUtil, OrcMetrics, and others

[HennesyChihiro]

This PR follows up on #15214 to fix further minor typos, grammatical errors, and Javadoc formatting issues discovered in the ORC package to improve code quality and readability.

Key changes include:

• ORCSchemaUtil: Fixed "convertion" to "conversion" and standardized apostrophe usage in Javadoc.
• OrcMetrics: Removed a redundant word in comments ("value number of values" -> "number of values").
• OrcFileAppender: Improved the phrasing of an estimated length comment.

[singhpk234]

Thanks @HennesyChihiro !

[huaxingao]

Thanks @HennesyChihiro for the PR! Thanks @singhpk234 for the review!