Bump payjoin version to 0.21.0

[DanGould]

We should really get #417, #373, and perhaps #413 in before release candidate in order to prevent future breaking changes

[coveralls]

Pull Request Test Coverage Report for Build 12132229311

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.04%) to 61.826%

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Files with Coverage Reduction	New Missed Lines	%
payjoin/src/send/mod.rs	2	92.78%

Totals
Change from base Build 12132019366:	-0.04%
Covered Lines:	2865
Relevant Lines:	4634

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💛 - Coveralls

[DanGould]

@nothingmuch I think we made it. I don't think we need an rc unless we need test utils in this one. what say you?

[spacebear21]

ACK 9d937bc