Drop dist source map to avoid rebase conflicts

[djkees]

Stops committing dist/index.js.map so consecutive PR merges no longer force every other open PR to rebase and rebuild dist/. See #271

• Remove --source-map from the build script
• Delete dist/index.js.map and dist/sourcemap-register.js
• Rebuild dist/index.js (only change: the sourcemap-register require and the sourceMappingURL comment are gone)
• verify dist needs no change since it diffs whatever dist/ contains
• Trade-off: crash stack traces point into the bundled dist/index.js instead of the source files; the map can be regenerated from any tag with --source-map
• Not a full fix: dist/index.js can still conflict when PRs touch nearby code

[djkees]

Rebased onto develop and force-pushed: Support lfortran 0.67.0 and Upgrade npm packages both rebuilt dist/index.js.map, which this PR deletes, so the PR hit the exact modify/delete conflict described in #271. Rebuilt dist/ after the rebase and it matches.

[minhqdao]

I think you can rerun the failed job, mark the PR as ready, and then we can merge it. As you mentioned in the description, it won't fully eliminate merge conflicts, but it should remove the conflict that occurred on every rebuild. We can give it a try and see how it goes.

[djkees]

Marked ready. I don't have rerun permissions here, so could you rerun the failed job? It's ifort / 2021.2 macos-26-intel, which failed on a DNS error reaching registrationcenter-download.intel.com (ENOTFOUND, then ESERVFAIL), unrelated to this change. verify dist passed on the previous run.