chore: drop now-unused @ts-expect-error directives in serializeData

Problem: tsc --build fails on upstream/main with three TS2578 "Unused
'@ts-expect-error' directive" errors at lib/index.js:233/235/237.
markdown-table's types now accept null for the align-delimiters,
padding, and string-length options, so the suppressions are obsolete
and the type checker now flags them.

Goal: restore tsc --build to a clean pass so the package's own test
suite runs end-to-end without an unrelated build failure.

Changes:
- lib/index.js: remove three @ts-expect-error comments around the
  alignDelimiters / padding / stringLength fields passed to
  markdownTable in serializeData.

Notes: drift from a markdown-table type update; verified npm test now
passes (build + format + 100% coverage + 32 of 32 tests dev and prod).

Author: ChristianMurphy

lib/index.js

@@ -230,11 +230,8 @@ export function gfmTableToMarkdown(options) {
   function serializeData(matrix, align) {
     return markdownTable(matrix, {
       align,
-      // @ts-expect-error: `markdown-table` types should support `null`.
       alignDelimiters,
-      // @ts-expect-error: `markdown-table` types should support `null`.
       padding,
-      // @ts-expect-error: `markdown-table` types should support `null`.
       stringLength
     })
   }