Update GitHub Actions to build with Python 3.12.0-rc.3 and fix linter…

… error

This occurs only with Py 12:

```
flake8 --ignore=E501,E126,W503 email_validator tests
email_validator/syntax.py:30:24: E231 missing whitespace after ':'
email_validator/syntax.py:32:24: E231 missing whitespace after ':'
```

See https://github.com/actions/python-versions/releases for the Python versions supported in GitHub Actions.

.github/workflows/test_and_build.yaml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11", "3.12.0-alpha.5"]
+        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11", "3.12.0-rc.3"]
 
     steps:
       - uses: actions/checkout@v3

email_validator/syntax.py

@@ -27,9 +27,9 @@ def safe_character_display(c):
 
     # Construct a hex string in case the unicode name doesn't exist.
     if ord(c) < 0xFFFF:
-        h = f"U+{ord(c):04x}".upper()
+        h = f"U+{ord(c): 04x}".upper()
     else:
-        h = f"U+{ord(c):08x}".upper()
+        h = f"U+{ord(c): 08x}".upper()
 
     # Return the character name or, if it has no name, the hex string.
     return unicodedata.name(c, h)