Fix supportedMethods property type

[1000ch]

According to https://www.w3.org/TR/payment-request/#paymentmethoddata-dictionary.

Fixes #19200.

[kitsonk]

This is not the proper way to contribute to these files.

As mentioned in the README in this directory:

Read This!

These files are not meant to be edited by hand.
If you need to make modifications, the respective files should be changed within the repository's top-level src directory.
Running jake LKG will then appropriately update the files in this directory.

And in the CONTRIBUTING.md:

Contributing lib.d.ts fixes

The library sources are in: src/lib

Library files in built/local/ are updated by running

jake

The files in lib/ are used to bootstrap compilation and usually do not need to be updated.

src/lib/dom.generated.d.ts and src/lib/webworker.generated.d.ts

These two files represent the DOM typings and are auto-generated. To make any modifications to them, please submit a PR to https://github.com/Microsoft/TSJS-lib-generator

[1000ch]

@kitsonk Fixed 🙏

[kitsonk]

@1000ch again... from the above:

src/lib/dom.generated.d.ts and src/lib/webworker.generated.d.ts

These two files represent the DOM typings and are auto-generated. To make any modifications to them, please submit a PR to https://github.com/Microsoft/TSJS-lib-generator

[1000ch]

@kitsonk Ahh, sorry again.