scripted-diff: Replace error() with LogError()

This fixes the log output when -logsourcelocations is used.

Also, instead of 'ERROR:', the log will now say '[error]', like other
errors logged with LogError.

-BEGIN VERIFY SCRIPT-
 sed -i --regexp-extended 's!  error\("([^"]+)"!  LogError("\1\\n"!g' $( git grep -l '  error(' ./src/ )
-END VERIFY SCRIPT-

src/script/signingprovider.cpp

@@ -158,7 +158,7 @@ bool FillableSigningProvider::GetKey(const CKeyID &address, CKey &keyOut) const
 bool FillableSigningProvider::AddCScript(const CScript& redeemScript)
 {
     if (redeemScript.size() > MAX_SCRIPT_ELEMENT_SIZE) {
-        error("FillableSigningProvider::AddCScript(): redeemScripts > %i bytes are invalid", MAX_SCRIPT_ELEMENT_SIZE);
+        LogError("FillableSigningProvider::AddCScript(): redeemScripts > %i bytes are invalid\n", MAX_SCRIPT_ELEMENT_SIZE);
         return false;
     }