Eliminate a nested if

Sonar is pointing out an if/if block, collapse the two to fix the issue
up.

Signed-off-by: Robert Varga <robert.varga@pantheon.tech>

Author: rovarga

triemap/src/main/java/tech/pantheon/triemap/INode.java

@@ -520,11 +520,9 @@ private void cleanParent(final Object nonlive, final INode<K, V> parent, final T
             final var sub = cn.array[pos];
             if (sub == this && nonlive instanceof TNode<?, ?> tn) {
                 final var ncn = cn.updatedAt(pos, tn.copyUntombed(), gen).toContracted(lev - LEVEL_BITS);
-                if (!parent.gcas(cn, ncn, ct)) {
-                    if (ct.readRoot().gen == startgen) {
-                        // Tail recursion: cleanParent(nonlive, parent, ct, hc, lev, startgen);
-                        continue;
-                    }
+                if (!parent.gcas(cn, ncn, ct) && ct.readRoot().gen == startgen) {
+                    // Tail recursion: cleanParent(nonlive, parent, ct, hc, lev, startgen);
+                    continue;
                 }
             }
             break;