fix(deps): add missing pycairo linux-x86_64 wheel hash to requirements.txt

## Problem

`requirements.txt` for `pip_rules_score` (and related hubs) is hash-pinned. The binary wheel for pycairo 1.29.0 on linux-x86_64 (`c6fe79e1325dacd7b367f1b4ead32ae35c733c6255f45dfcd1467e5ec0ee274a`) is missing from the hash list. pip cannot verify that wheel, skips it, falls back to the sdist, and attempts a source build — which fails in environments without `cairo` development headers (e.g. hermetic Bazel sandbox, minimal CI containers).

## Proposed Change

Add the missing wheel hash to `bazel/rules/rules_score/requirements.txt`:

```
pycairo==1.29.0 --hash=sha256:09b7f69a5ff6881e151354ea092137b97b0b1f0b2ab4eb81c92a02cc4a08e335 + --hash=sha256:c6fe79e1325dacd7b367f1b4ead32ae35c733c6255f45dfcd1467e5ec0ee274a ...
```

## Motivation

With the hash present pip selects the pre-built binary wheel and no system headers are required.

Open bazel/rules/rules_score/requirements.txt and locate the pycairo==1.29.0 hash list. Add the specified linux-x86_64 wheel hash, then verify that the pinned dependency can select the wheel without falling back to a source build.

Written by the indexing model from the issue text.