Does JsonSchemaExporter handle decimal pattern correctly?

### Description

```csharp
using System;
using System.Text.Json;
using System.Text.Json.Schema;
using System.Text.Json.Serialization;

var x = new JsonSerializerOptions();
x.WriteIndented = true;
x.TypeInfoResolver = JsonSerializerOptions.Default.TypeInfoResolver;
x.NumberHandling = JsonNumberHandling.AllowReadingFromString | JsonNumberHandling.WriteAsString;
x.Converters.Add(new JsonStringEnumConverter());

Console.WriteLine(JsonSchemaExporter.GetJsonSchemaAsNode(x, typeof(decimal)).ToJsonString(x));

Console.WriteLine(JsonSerializer.Deserialize("\"1E4\"", x));

```

### Reproduction Steps

See above.

The deserialization of `"1E4"` works and prints `10000`, but the pattern produced doesn't seem to handle the exponent syntax.

The produced schema today is:

```
{
"type": [
"string",
"number"
],
"pattern": "^-?(?:0|[1-9]\\d*)(?:\\.\\d\u002B)?$"
}
```

### Expected behavior

Pattern should allow `1E4`

### Actual behavior

It doesn't

### Regression?

_No response_

### Known Workarounds

_No response_

### Configuration

_No response_

### Other information

_No response_