`DefaultCharset` false negative in method-reference

### Error Prone version

2.49.0 (error_prone_core)

### Check name

DefaultCharset

### Description

Both forms create an `InputStreamReader` without specifying a charset, so both should trigger `DefaultCharset`. However, Error Prone reports the lambda form but misses the equivalent constructor method reference `InputStreamReader::new`. Since both forms call the same constructor, the method-reference case is a false negative.

### Reproducer

```java
package demo;

import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Optional;

public class DefaultEncodingUsageCheck {

public void streamUsage(String resourcePath) throws IOException {
try (var is = DefaultEncodingUsageCheck.class.getResourceAsStream(resourcePath)) {

// BEFORE — NOT flagged by DefaultCharset (false negative)
Optional.ofNullable(is)
.map(InputStreamReader::new)
.map(reader -> reader.hashCode() + 1);

// AFTER — flagged by DefaultCharset
Optional.ofNullable(is)
.map(is2 -> new InputStreamReader(is2))
.map(reader -> reader.hashCode() + 1);
}
}
}
```

### Actual behavior

`DefaultCharset` fires only on the lambda form; the method reference form is not reported.