Remove redundant JSDoc flag checks

[jakebailey]

These are redundant; JSDoc and EagerJSDoc both check this and return nil.

[Copilot]

Pull request overview

This PR removes redundant NodeFlagsHasJSDoc guard checks at several call sites by relying on ast.Node.JSDoc / ast.Node.EagerJSDoc to short-circuit and return nil when JSDoc is not present.

Changes:

• Simplify selection range traversal to always iterate current.JSDoc(sourceFile) without a separate flag check.
• Simplify checker JSDoc comment validation to always iterate node.EagerJSDoc(nil) without a separate flag check.
• Simplify AST navigation helpers that visit children + JSDoc to always iterate node.JSDoc(sourceFile) without a separate flag check.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
internal/ls/selectionranges.go	Removes redundant HasJSDoc check before iterating JSDoc nodes during selection range computation.
internal/checker/checker.go	Removes redundant HasJSDoc check before iterating eager JSDoc nodes during source element checking.
internal/astnav/tokens.go	Removes redundant HasJSDoc check in VisitEachChildAndJSDoc.
internal/ast/utilities.go	Removes redundant HasJSDoc check in ForEachChildAndJSDoc.