astro: Remove deprecated sourceMapsUploadOptions build option #23624

@sentry/astro still accepts the deprecated sourceMapsUploadOptions build option. The other meta-framework SDKs dropped theirs for v11, so astro is the last one carrying it.

Current state

• packages/astro/src/integration/types.ts:163 still declares sourceMapsUploadOptions?: SourceMapsOptions, marked @deprecated with "Please move the options to the top-level configuration".
• The deprecation landed in feat(astro): Align options with shared build time options type #17396 (feat(astro): Align options with shared build time options type), which was v10-era work.
• The v11 removal sweep covered sveltekit (feat(sveltekit)!: Remove deprecated sourceMapsUploadOptions Vite plugin option #22874) and nuxt (feat(nuxt)!: Remove deprecated sourceMapsUploadOptions module option #22875) but skipped astro.

Astro's other v11 build-option cleanup was done piecemeal, which is likely how this slipped: unstable_sentryVitePluginOptions was handled in #23342 and release / debug in #22248, but nothing covered this option.

What to do

Remove sourceMapsUploadOptions from sentryAstro() and have users move its fields to the top level, matching solidstart, react-router, nuxt and sveltekit. Note that enabled is replaced by sourcemaps.disable (inverted) in the other SDKs, so astro should follow the same shape.

Migration guide

MIGRATION.md currently scopes the "Meta-framework build options" entry to nuxt and sveltekit, which is accurate today. Add astro to that entry as part of this change.