fix: Add license information to pyproject.toml (#16816)

Add license specifiers according to
https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#license-and-license-files

This allows automatic license inspection tools like pip-licenses to
correctly categorize this package.

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- [ ] Appropriate docs were updated (if necessary)

Towards #16603 🦕

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
Co-authored-by: Anthonios Partheniou <partheniou@google.com>

Author: 3 people

packages/google-crc32c/pyproject.toml

@@ -22,3 +22,4 @@ version = "1.8.0"
 description = "A python wrapper of the C library 'Google CRC32C'"
 readme = "README.md"
 requires-python = ">=3.8"
+license = {text = "Apache-2.0"}