SPDX Failing to parse license for no obvious reason

Hi `license-expression`. I must begin that this is a great piece of software, and I'm grateful for your contributions.

I noticed a strange edge case when using the spdx license parser. The parser raises an exception when I try to parse `Sleepycat License` but is fine with `Sleepydog License` or even `Sleepyca License`.

Reproducible example:
```python
SPDX_LICENSING = license_expression.get_spdx_licensing()

# ExpressionParseError: Invalid symbols sequence such as (A B) for token: "License" at position: 10
_ = SPDX_LICENSING.parse('Sleepycat License')

# Works
_ = SPDX_LICENSING.parse('Sleepydog License')
_ = SPDX_LICENSING.parse('Sleepyca License')
```

Relevant versions installed via conda.
```bash
python 3.11.4 h47c9636_0_cpython conda-forge
license-expression 30.1.1 pyhd8ed1ab_0 conda-forge
```

Thanks in advance!