Revert PyPy switch to 3.11.

At least 1 test fails trying to build cryptography with:
```
...
pip:     cargo:rerun-if-env-changed=PYO3_CROSS
pip:     cargo:rerun-if-env-changed=PYO3_CROSS_LIB_DIR
pip:     cargo:rerun-if-env-changed=PYO3_CROSS_PYTHON_VERSION
pip:     cargo:rerun-if-env-changed=PYO3_CROSS_PYTHON_IMPLEMENTATION
pip:     cargo:rerun-if-env-changed=PYO3_PRINT_CONFIG
pip:
pip:     --- stderr
pip:     error: the configured PyPy interpreter version (3.11) is newer than PyO3's maximum supported version (3.10)
pip:     = help: please check if an updated version of PyO3 is available. Current version: 0.23.2
...
```

See: https://github.com/PyO3/pyo3/issues/4689x

.github/workflows/ci.yml

@@ -76,7 +76,7 @@ jobs:
           - tox-env: py311-pip23_3_2
           - tox-env: py313-pip25_0
           - tox-env: py314-pip25_0
-          - tox-env: pypy311-pip24_3_1
+          - tox-env: pypy310-pip24_3_1
 
           # Integration tests, split most into two shards:
           # ----------------------------------------------
@@ -104,9 +104,9 @@ jobs:
           - tox-env: py314-pip25_0-integration
             pex-test-pos-args: --shard 2/2
 
-          - tox-env: pypy311-pip24_3_1-integration
+          - tox-env: pypy310-pip24_3_1-integration
             pex-test-pos-args: --shard 1/2
-          - tox-env: pypy311-pip24_3_1-integration
+          - tox-env: pypy310-pip24_3_1-integration
             pex-test-pos-args: --shard 2/2
     steps:
       - name: Free Up Disk Space