bug: IonRouterOutlet canGoBack() return always return false

# Bug Report

**Ionic version:**

[x] **4.6.1 / 4.6.2**

**Current behavior:**

ActivatedRoute canGoBack() always return false

**Expected behavior:**

canGoBack() should return correctly

**Steps to reproduce:**

**Related code:**

```
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```

**Other information:**

**Ionic info:**

```
insert the output from ionic info here
```

The issue identifies IonRouterOutlet and ActivatedRoute as the relevant entry points, but provides no reproduction steps, sample code, files, or tests. Start by locating the canGoBack() implementation and related router tests; done means reproducing the reported navigation state and verifying that canGoBack() returns the correct value.

由索引模型根据 Issue 内容生成。