Update peerDependency on Typescript to ~3.9.x

[bjornharvold]

Cannot update to Angular 10 with forcing an ng update at the moment.

ng update @angular/core @angular/cli fails

Have to type
ng --force update @angular/core @angular/cli

[lauraharker]

I believe @rrdelaney is working on upgrading to TS3.9.

Created Google internal issue http://b/159923702.

[aramperes]

Please bump this ticket when a new version of tsickle is released. Thanks for the quick turnaround!

[rrdelaney]

New version should be published!

[aramperes]

Looking at https://registry.npmjs.org/tsickle (versions -> 0.39.0 -> peerDependencies), the TypeScript peerDependency is still at ~3.8.2. Only the devDependency seems to have been updated.

[rrdelaney]

Sorry about that, should be fixed! Thanks for the PR!