Fix the hard coded epoch that we need to wait for.

Before it waited for a hard coded amount 7, which is not correct. In
reality it should be waiting until 13, seen from this string

Amount 412 withdrawable starting from epoch 13

However even if this changes in the future, this regex will correctly
get it.

tests/src/e2e/ledger_tests.rs

@@ -2202,7 +2202,7 @@ fn pos_rewards() -> Result<()> {
 /// 3. Wait for epoch 4
 /// 4. Submit another delegation to the genesis validator
 /// 5. Submit an unbond of the delegation
-/// 6. Wait for epoch 7
+/// 6. Wait for epoch withdraw_epoch
 /// 7. Check the output of the bonds query
 #[test]
 fn test_bond_queries() -> Result<()> {
@@ -2317,6 +2317,11 @@ fn test_bond_queries() -> Result<()> {
     ];
     let mut client = run!(test, Bin::Client, tx_args, Some(40))?;
     client.exp_string("Transaction is valid.")?;
+    let (_, res) = client
+        .exp_regex(r"withdrawable starting from epoch [0-9]+")
+        .unwrap();
+    let withdraw_epoch =
+        Epoch::from_str(res.split(' ').last().unwrap()).unwrap();
     client.assert_success();
 
     // 6. Wait for epoch 7
@@ -2327,7 +2332,7 @@ fn test_bond_queries() -> Result<()> {
             panic!("Timed out waiting for epoch: {}", 7);
         }
         let epoch = get_epoch(&test, &validator_one_rpc)?;
-        if epoch >= Epoch(7) {
+        if epoch >= withdraw_epoch {
             break;
         }
     }