Fix re-exports for SAS.ts (#3405)
These three are only types, not objects we can export.
Fixes warnings in EW (and probably some build failures for someone somewhere):
```
2023-05-24 11:27:28.294 [element-js] WARNING in ../matrix-js-sdk/src/crypto/verification/SAS.ts 31:0-123
2023-05-24 11:27:28.294 [element-js] "export 'EmojiMapping' was not found in '../../crypto-api/verification'
2023-05-24 11:27:28.294 [element-js]
2023-05-24 11:27:28.294 [element-js] WARNING in ../matrix-js-sdk/src/crypto/verification/SAS.ts 31:0-123
2023-05-24 11:27:28.294 [element-js] "export 'GeneratedSas' (reexported as 'IGeneratedSas') was not found in '../../crypto-api/verification'
2023-05-24 11:27:28.294 [element-js]
2023-05-24 11:27:28.294 [element-js] WARNING in ../matrix-js-sdk/src/crypto/verification/SAS.ts 31:0-123
2023-05-24 11:27:28.294 [element-js] "export 'ShowSasCallbacks' (reexported as 'ISasEvent') was not found in '../../crypto-api/verification'
```
