Fix phylocanvas visualization build

[davelopez]

Attempt to fix:

Building phylocanvas
$ parcel build src/script.js --dist-dir static
Building...
🚨 Build failed.

@parcel/core: Failed to resolve 'buffer' from 
'./node_modules/@loaders.gl/loader-utils/dist/esm/lib/filesystems/readable-file.js'
  /home/runner/work/galaxy/galaxy/galaxy root/config/plugins/visualizations/phylocanvas/node_modules/@loaders.gl/loader-utils/dist/esm/lib/filesystems/readable-file.js:15:54
    14 |       return Buffer.from(arrayBuffer);
  > 15 |     },
  >    |       ^
    16 |     close: async () => {},
    17 |     size: blob.size


@parcel/resolver-default: Node builtin polyfill "buffer/" is not installed, but 
auto install is disabled.
  /home/runner/work/galaxy/galaxy/galaxy root/config/plugins/visualizations/phylocanvas/node_modules/@loaders.gl/loader-utils/src/lib/filesystems/readable-file.ts:15:54
    14 |     return {
  > 15 | ) => Buffer.from(data, start, length),
  >    |      ^^^^^^ used here
    16 |       close: async () => {},
    17 |       size: arrayBuffer.byteLength


  💡 Install the "buffer/" package with your package manager, and run Parcel 
     again.

Those visualizations will hopefully be soon migrated to the pre-built system, this is just an attempt to keep the tests in the dev branch working.

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[github-actions]

This PR was merged without a "kind/" label, please correct.