fix verify-hardcoded-versions issues (rapidsai#21770)

Fixes this `pre-commit` error on `release/26.04`:

```text
In file RAPIDS_BRANCH:1:9:
 release/26.04
warning: do not hard-code version, read from VERSION file instead
```

And this one on `main`:

```text
In file python/cudf/cudf/tests/dataframe/test_binops.py:677:24:
         lambda: [25.5, 26.6, 27.7, 28.8],
warning: do not hard-code version, read from VERSION file instead
```

See rapidsai/pre-commit-hooks#121 for details

Authors:
  - James Lamb (https://github.com/jameslamb)

Approvers:
  - Lawrence Mitchell (https://github.com/wence-)
  - Bradley Dice (https://github.com/bdice)

URL: rapidsai#21770

Author: jameslamb

.pre-commit-config.yaml

@@ -272,7 +272,9 @@ repos:
             (^|/)pom[.]xml$|
             ^[.]pre-commit-config[.]yaml$|
             ^conda/environments/|
+            RAPIDS_BRANCH$|
             [.](md|rst|avro|parquet|png|orc|gz|pkl|sas7bdat)$|
+            ^python/cudf/cudf/tests|
             ^python/cudf/cudf/VERSION$
       - id: verify-pyproject-license
         # ignore the top-level pyproject.toml, which doesn't