fix(mcp): distinguish execute_sql permission from write access in instructions

Remove 'or running SQL' from the write-operations bullet so that SQL
execution is not grouped under can_write. execute_sql is controlled by
the separate execute_sql_query permission on SQLLab, which is already
called out in its own bullet below.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>