Fix leftover use of divModWithSlacks in doc

The option `divModWithSlacks` was previously changed to `divModNoSlacks`.
However, this was not reflected in the documentation.

Author: david-k

docs/using-the-compiler.rst

@@ -410,12 +410,13 @@ Input Description
             "source1.sol": ["contract1"],
             "source2.sol": ["contract2", "contract3"]
           },
-          // Choose whether division and modulo operations should be replaced by
-          // multiplication with slack variables. Default is `true`.
-          // Using `false` here is recommended if you are using the CHC engine
+          // Choose how division and modulo operations should be encoded.
+          // When using `false` they are replaced by multiplication with slack
+          // variables. This is the default.
+          // Using `true` here is recommended if you are using the CHC engine
           // and not using Spacer as the Horn solver (using Eldarica, for example).
           // See the Formal Verification section for a more detailed explanation of this option.
-          "divModWithSlacks": true,
+          "divModNoSlacks": false,
           // Choose which model checker engine to use: all (default), bmc, chc, none.
           "engine": "chc",
           // Choose which types of invariants should be reported to the user: contract, reentrancy.