Remove repeat and enforce-determinism options

These only functioned if a very narrow combination of conditions held:

- The result path does not yet exist (--check did not result in
  repeated builds), AND
- The result path is not available from any configured substituters, AND
- No remote builders that can build the path are available.

If any of these do not hold, a derivation would be built 0 or 1 times
regardless of the repeat option. Thus, remove it to avoid confusion.

src/libstore/legacy-ssh-store.cc

@@ -255,8 +255,8 @@ private:
                 << settings.maxLogSize;
         if (GET_PROTOCOL_MINOR(conn.remoteVersion) >= 3)
             conn.to
-                << settings.buildRepeat
-                << settings.enforceDeterminism;
+                << 0 // buildRepeat hasn't worked for ages anyway
+                << 0;
 
         if (GET_PROTOCOL_MINOR(conn.remoteVersion) >= 7) {
             conn.to << ((int) settings.keepFailed);