Fix lock_api feature name for RawRwLockUpgradeDowngrade

[cavivie]

Changes:

• Rename old feature namelock_api1 to new feature name lock_api (I guess this has been forgotten?).
• Should import lock_api_crate as the package name instead of external lock_api crate dependency.
• Associated type of phantom data of RwLock requires that it already implement the RelaxStrategy trait.