Fix grammar checking for in and out modifiers in @template tags

[ahejlsberg]

Fixes #4076.

[Copilot]

Pull request overview

Fixes TypeScript-Go’s grammar checking to correctly allow in/out modifiers on type parameters originating from JSDoc @template tags when those templates are attached to JSDoc-derived type aliases (e.g. @typedef), matching upstream TypeScript behavior.

Changes:

• Update checkGrammarModifiers to treat ast.KindJSTypeAliasDeclaration the same as a regular type alias for validating in/out modifiers.
• Remove the unused isJSDocTypedefTag stub and related commented-out porting notes.
• Update submodule conformance baselines for jsdocTemplateTag8 to remove the spurious TS1274 errors (and delete the now-empty .diff).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
internal/checker/grammarchecks.go	Accept IsTypeOrJSTypeAliasDeclaration as a valid container for in/out modifier grammar checks on type parameters.
testdata/baselines/reference/submodule/conformance/jsdocTemplateTag8.errors.txt	Baseline updated to reflect removal of incorrect TS1274 diagnostics.
testdata/baselines/reference/submodule/conformance/jsdocTemplateTag8.errors.txt.diff	Removed since there is no longer a difference vs the reference baseline for this test.