remove lazy-pos forceValue

almost all uses of this are interactive, except for deepSeq. deepSeq is
going to be expensive and rare enough to not care much about, and
Value::determinePos should usually be cheap enough to not be too much of
a burden in any case.

src/libcmd/installable-flake.cc

@@ -52,7 +52,7 @@ Value * InstallableFlake::getFlakeOutputs(EvalState & state, const flake::Locked
     auto aOutputs = vFlake->attrs->get(state.symbols.create("outputs"));
     assert(aOutputs);
 
-    state.forceValue(*aOutputs->value, [&]() { return aOutputs->value->determinePos(noPos); });
+    state.forceValue(*aOutputs->value, aOutputs->value->determinePos(noPos));
 
     return aOutputs->value;
 }