Fix DER 144 signature test

The test for multiple formats has invalid input. Find the following code in `signatures.spec.ts`:

```
// der144Signature
"3045022100f6d3aefb132b74e879a937dc6a28003d6c2acee6e27291bfb24834aa2cd2a610022003a06b8f150ab71b3e19621114f98416417bea4fbc5b3b4a30b610fea9f281e1"
```

It’s actually der142 (not 144), the length is the same as the prev signature in the test. The test case needs to be fixed by providing valid DER 144-length signature.

Open signatures.spec.ts and locate the multiple-formats test and its der144Signature fixture. Replace the invalid DER 142-length value with a valid DER 144-length signature, then run the relevant signature test to confirm the fixture is accepted.

Written by the indexing model from the issue text.