remove unused GetDestinationForKey

It is only used in test. There it is problematic, because it sometimes
relies on m_default_address_type. If the default were changed to
BECH32M, those tests would fail the assert(false).

So just use PKHash{} in all tests and remove GetDestinationForKey.

src/outputtype.cpp

@@ -46,27 +46,6 @@ const std::string& FormatOutputType(OutputType type)
     assert(false);
 }
 
-CTxDestination GetDestinationForKey(const CPubKey& key, OutputType type)
-{
-    switch (type) {
-    case OutputType::LEGACY: return PKHash(key);
-    case OutputType::P2SH_SEGWIT:
-    case OutputType::BECH32: {
-        if (!key.IsCompressed()) return PKHash(key);
-        CTxDestination witdest = WitnessV0KeyHash(key);
-        CScript witprog = GetScriptForDestination(witdest);
-        if (type == OutputType::P2SH_SEGWIT) {
-            return ScriptHash(witprog);
-        } else {
-            return witdest;
-        }
-    }
-    case OutputType::BECH32M:
-    case OutputType::UNKNOWN: {} // This function should never be used with BECH32M or UNKNOWN, so let it assert
-    } // no default case, so the compiler can warn about missing cases
-    assert(false);
-}
-
 CTxDestination AddAndGetDestinationForScript(FlatSigningProvider& keystore, const CScript& script, OutputType type)
 {
     // Add script to keystore