fix: Unpin mysqlclient and require >=2.2.0

[chrisburr]

Fixes #190.

The <2.1 constraint was added in 4ca5a1b because mysqlclient 2.1 removed the module-level MySQLdb.escape_string. DIRAC stopped using it in v8.0.81, v9.0.23 and v9.1.13 (all released 2026-07-06/07), so the constraint is no longer needed.

Requires >=2.2.0 rather than simply dropping the upper bound because:

• cursor.mogrify — the feature originally requested in Updating mysqlclient? #190 — was added in 2.2.0.
• The diracgrid channel only carries 2.0.3, which would otherwise win over conda-forge on channel priority.
• conda-forge only has 2.0.3 builds up to py311, so keeping the pin means rebuilding 2.0.3 in the diracgrid channel for every new Python. conda-forge 2.2.8 already ships py314 builds for all four target platforms.

Note this raises the minimum DIRAC version to v8.0.81 / v9.0.23 / v9.1.13. Older releases still call the removed module-level escape_string from ComponentInstaller.py; the query path in MySQL.py used the connection.escape_string method, which still exists in 2.2.8, so the impact on an out-of-date client is limited to server-side database creation and fails loudly.

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CHANGE: Require mysqlclient >=2.2.0, making cursor.mogrify available

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