build: rm "dataclasses" from pinned requirements-hw.txt

trezorlib requires "dataclasses ; python_version<'3.7'", and our min supported python version is 3.6,
so freeze_packages.sh pins down a version of "dataclasses". However, when creating binaries we
use newer versions of python (typically py3.9 atm), for which dataclasses is not available (it's a backport of py3.7 stuff).
Hmhm, what to do... short-term, I am manually removing the dataclasses pin, so it won't be installed in our binaries.

```
Collecting construct==2.10.67
  Downloading construct-2.10.67.tar.gz (57 kB)
     |████████████████████████████████| 57 kB 2.7 MB/s
  Preparing metadata (setup.py) ... done
Requirement already satisfied: cryptography==36.0.1 in ./build/appimage/electrum.AppDir/usr/lib/python3.9/site-packages (from -r /opt/electrum/contrib/build-linux/appimage/../../../contrib/deterministic-build/requirements-hw.txt (line 74)) (36.0.1)
ERROR: Could not find a version that satisfies the requirement dataclasses==0.8 (from versions: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6)
ERROR: No matching distribution found for dataclasses==0.8
```

contrib/deterministic-build/requirements-hw.txt

@@ -92,9 +92,6 @@ cryptography==36.0.1 \
     --hash=sha256:e0344c14c9cb89e76eb6a060e67980c9e35b3f36691e15e1b7a9e58a0a6c6dc3 \
     --hash=sha256:ebc15b1c22e55c4d5566e3ca4db8689470a0ca2babef8e3a9ee057a8b82ce4b1 \
     --hash=sha256:ec63da4e7e4a5f924b90af42eddf20b698a70e58d86a72d943857c4c6045b3ee
-dataclasses==0.8 \
-    --hash=sha256:0201d89fa866f68c8ebd9d08ee6ff50c0b255f8ec63a71c16fda7af82bb887bf \
-    --hash=sha256:8479067f342acf957dc82ec415d355ab5edb7e7646b90dc6e2fd1d96ad084c97
 ecdsa==0.17.0 \
     --hash=sha256:5cf31d5b33743abe0dfc28999036c849a69d548f994b535e527ee3cb7f3ef676 \
     --hash=sha256:b9f500bb439e4153d0330610f5d26baaf18d17b8ced1bc54410d189385ea68aa