fix: invalid syntax for ClassAutoAccessorDescriptor

[rwaskiewicz]

add a colon immediately following to the value#set property

prior to this change, this type would be considered invalid typescript syntax

':' expected.(1005)

TS Playground showing the errors surfaced by the type checker: https://www.typescriptlang.org/play?target=99#code/C4TwDgpgBAwgNgQwM5IIIFdgHtUGNcQpYBOAIhLiQtsVALxQAUAUFFAG4JzoQBcUAb1ZsoAcwjB+jAJT0AfFHQA7ANZKsAdyUBuYWyQTGnbn0Wr1W2XQXssASwAmutgF8ANMMpLgEAB6TBPSgVOyUHfgAiBHxCJBII5xElBABbUyRgYlDRKAAfKCQQFIAjLDhEtmiCFH4BMUNpfmU1TSU3AsNjHibzVsaOewcoFwqC4Go7XH5SsogEHSCwLM4faaxZ+dGEBwcASSU7YDsuOwAvCGJGUMPjuDOLqSsbQf7bR0SXZifAtnFgAH5HvIzC0tIkDACpF1TM0LEpvm8nMJrpCmCjbgA1LjdEFw76w1q6Fx5AbvIA