`RoutineCache` was not used, remove it.
Rename `RoutineCacheT` to the now unused name `RoutineCache`.

Bug: b/126126820
Change-Id: I656c1727446754b2063033806634678b14485b6f
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/43816Tested-by: Ben Clayton <bclayton@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>