Gazelle generates py_proto_library with imports attribute when in a non-root python_root

# 🐞 bug report

### Affected Rule

`gazelle`

### Is this a regression?

No, I believe it's a new feature introduced by https://github.com/bazel-contrib/rules_python/issues/2994 and it seems to be not working as expected in the specific situation of this report.

### Description

When using gazelle to generate [`py_proto_library`](https://github.com/bazel-contrib/rules_python/issues/2994), it doesn't work as expected when the proto file is in a subfolder of a python root that differs from the repo root (specified with the directive `# gazelle:python_root`).

Gazelle generates the target with an `imports` attribute, which is not supported and thus the target fails to build.

## 🔬 Minimal Reproduction

https://github.com/regb/issue-reports/tree/main/rules_python/py_proto_imports

## 🔥 Exception or Error

Gazelle runs smoothly but generates the invalid targets, then running build generate this error:

$ bazel build ...

ERROR: /home/regb/vcs/issue-reports/rules_python/py_proto_imports/src/mypackage/BUILD.bazel:10:17: //src/mypackage:example_py_pb2: no such attribute 'imports' in 'py_proto_library' rule

ERROR: package contains errors: src/mypackage

ERROR: package contains errors: src/mypackage: //src/mypackage:example_py_pb2: no such attribute 'imports' in 'py_proto_library' rule

WARNING: Target pattern parsing failed.

ERROR: Skipping '...': Error evaluating '...': error loading package 'src/mypackage': Package 'src/mypackage' contains errors

ERROR: Error evaluating '...': error loading package 'src/mypackage': Package 'src/mypackage' contains errors

INFO: Elapsed time: 0.136s

INFO: 0 processes.

ERROR: Build did NOT complete successfully

## 🌍 Your Environment

**Operating System:**

  

    Ubuntun 22.04

  

**Output of `bazel version`:**

  

    8.5.0

  

**Rules_python version:**

  

    1.7.0 (also tested 1.6.3)

  

从 regb/issue-reports/rules_python/py_proto_imports 中的最小复现开始，检查 src/mypackage 下生成的 BUILD.bazel，重点关注 # gazelle:python_root 指令和生成的 py_proto_library 目标。运行 Gazelle，然后运行 bazel build ...；当生成的目标不再包含不受支持的 imports 属性且构建成功时，即表示完成。

由索引模型根据 Issue 内容生成。