Correctly find R in registry when first key searched is not found

[cderv]

I think this is needed for this to correctly work

quarto-cli/src/core/registry.ts

Lines 21 to 24 in d29e5da

	const val = registryReadString(r, key, value);
	if (val !== undefined) {
	return val;
	}

Otherwise val will be a Promise and val !== undefined not what it expected

This issue appeared following 966fd98 as HKCU does not have the key, but HKLM does. At least on my computer as I got

❯ quarto check knitr
[>] Checking R installation...........(None)

      Unable to locate an installed version of R.
      Install R from https://cloud.r-project.org/

This does not solve probably #1225 but related to its debugging.

Adding an await here makes sense right ?