Inconsistency in StringBuilder.Equals(StringBuilder) documentation regarding Capacity comparison

### Type of issue

Outdated article

### Description

There is a documentation mismatch in the `StringBuilder.Equals(StringBuilder)` method page. The "Returns" section and the "Example" output contradict the "Remarks" section for modern .NET versions (.NET Core 3.0+ and .NET 5+).

**The Inconsistency:**

1. **Returns Section:** It states that the method returns `true` if the instance and `sb` have equal string, `Capacity`, and `MaxCapacity`. This is only true for .NET Framework.
2. **Example Output:** The example shows that when `Capacity` is changed (in step `b4`), the result is `False`.
```csharp
// Current doc says:
b4) sb1 equals sb2: False

```

3. **Actual Behavior:** In modern .NET (Core 3.0+), the source code confirms that `Capacity` is **ignored**. Running the same example on .NET 6/7/8/9 results in `True` for step `b4`.

**Source Code Reference:**
As seen in the implementation, the method only iterates through chunks to compare characters and checks the `Length` property, but never accesses the `Capacity` property.

**Expected Documentation Update:**

* The **Returns** section should be updated to clarify that `Capacity` is not considered in modern .NET.
* The **Example Output** should be updated to reflect the behavior of current .NET versions where content equality is what matters.

### Page URL

https://learn.microsoft.com/en-us/dotnet/api/system.text.stringbuilder.equals?view=net-10.0#system-text-stringbuilder-equals(system-text-stringbuilder)

### Content source URL

https://github.com/dotnet/dotnet-api-docs/blob/main/xml/System.Text/StringBuilder.xml

### Document Version Independent Id

c7e78992-eaf2-dfb2-9b1f-2a2a76297c19

### Platform Id

cdcb8c19-bd84-2cd1-1cbf-47c5b6effd16

### Article author

@dotnet-bot