This pull request replaces the included <wallet/crypter.h> header in src/bench/ccoins_caching.cpp with <keystore.h> because only the latter is required.

For context see:

• Bitcoin developer notes:

Every .cpp and .h file should #include every header file it directly uses classes, functions or other definitions from, even if those headers are already included indirectly through other headers.

• SF.10 Avoid dependencies on implicitly included names

Avoid surprises. Avoid having to change #includes if an #included header changes. Avoid accidentally becoming dependent on implementation details and logically separate entities included in a header.