Replaced deprecated methods with recommended alternatives

[Pushkar-Mahajan4]

1. Replaced deprecated ANTLRException with IllegalArgumentException as recommended by ANTLRException document
2. Replace deprecated IOUtils.toString(final InputStream input) with recommended toString(input, Charset.defaultCharset())

Testing done

N/A

Proposed changelog entries

N/A

Proposed changelog category

/label skip-changelog

Proposed upgrade guidelines

N/A

Submitter checklist

• The Jira issue, if it exists, is well-described.
• The changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developers, depending on the change) and are in the imperative mood (see examples). Fill in the Proposed upgrade guidelines section only if there are breaking changes or changes that may require extra steps from users during upgrade.
• There is automated testing or an explanation as to why this change has no tests.
• New public classes, fields, and methods are annotated with @Restricted or have @since TODO Javadocs, as appropriate.
• New deprecations are annotated with @Deprecated(since = "TODO") or @Deprecated(forRemoval = true, since = "TODO"), if applicable.
• New or substantially changed JavaScript is not defined inline and does not call eval to ease future introduction of Content Security Policy (CSP) directives (see documentation).
• For dependency updates, there are links to external changelogs and, if possible, full differentials.
• For new APIs and extension points, there is a link to at least one consumer.

Desired reviewers

N/A

Before the changes are marked as ready-for-merge:

Maintainer checklist

• There are at least two (2) approvals for the pull request and no outstanding requests for change.
• Conversations in the pull request are over, or it is explicit that a reviewer is not blocking the change.
• Changelog entries in the pull request title and/or Proposed changelog entries are accurate, human-readable, and in the imperative mood.
• Proper changelog labels are set so that the changelog can be generated automatically.
• If the change needs additional upgrade steps from users, the upgrade-guide-needed label is set and there is a Proposed upgrade guidelines section in the pull request title (see example).
• If it would make sense to backport the change to LTS, a Jira issue must exist, be a Bug or Improvement, and be labeled as lts-candidate to be considered (see query).

[A1exKH]

LGTM.

[damianszczepanik]

Resolve issues reported by the linter locally, build locally then push fix to this PR

[NotMyFault]

See comments

[Copilot]

Pull Request Overview

This PR modernizes deprecated API usage by replacing outdated methods with their recommended alternatives. The changes focus on improving code maintainability by migrating away from deprecated APIs that may be removed in future versions.

• Replaced deprecated ANTLRException with IllegalArgumentException in exception handling documentation
• Replaced deprecated IOUtils.toString() with modern InputStream.readAllBytes() for stream processing

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
core/src/main/java/hudson/scheduler/CronTabList.java	Added deprecation warning comment about exception type change
core/src/main/java/hudson/os/WindowsUtil.java	Replaced IOUtils.toString() with readAllBytes() and removed unused import

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