Allow reading of immutables during construction time

test/libsolidity/syntaxTests/immutable/ctor_initialization_indirect_reading.sol

@@ -7,4 +7,4 @@ contract C {
     function f() public pure returns (uint) { return 3 + x; }
 }
 // ----
-// TypeError 7733: (136-137): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.
+// TypeError 7733: (136-137): Immutable variables cannot be read before they are initialized.