Fix missing 'packaging' requirement

The `sqlalchemy` instrumentation uses the `packaging` library to parse
the `sqlalchemy` SemVer.

`packaging` is not part of the standard library and should be included
in the `setup.cfg` file to avoid:

```
ModuleNotFoundError: No module named 'packaging'
```

Author: mattoberle

Diff for: instrumentation/opentelemetry-instrumentation-sqlalchemy/setup.cfg

@@ -41,6 +41,7 @@ install_requires =
     opentelemetry-api ~= 1.3
     opentelemetry-semantic-conventions == 0.24b0
     opentelemetry-instrumentation == 0.24b0
+    packaging >= 21.0
     wrapt >= 1.11.2
 
 [options.extras_require]