fixDependencies task loses exclusions when changing configuration

**Plugin version**
3.6.1

**Gradle version**
9.0.0

**JDK version**
21

**Describe the bug**
An existing dependency is configured as
```
api(project(":myProject")) {
exclude(group = "another project", module = "another module")
}
```

The `fixDependencies` task decides that this should be an `implementation` configuration instead. However when it runs it drops the exclude block so we get
```
implementation(project(":myProject"))
```

**To Reproduce**
1. Add a dependency with `api` configuration (which should be an `implementation` configuration) and an `exclude` block
2. Run `gradle fixDependencies`

**Expected behavior**
The `exclude` block should be maintained, so we should get an output
```
implementation(project(":myProject")) {
exclude(group = "another project", module = "another module")
}
```

Start at the fixDependencies task and trace how it rewrites an api dependency to implementation, focusing on how the existing exclude block is represented and preserved. Reproduce the issue with the Gradle command from the report; done means the generated implementation dependency retains the exclude block shown in the expected output.

Written by the indexing model from the issue text.