Docs: Feedback for Filtering Members with Attributes

Hi, I have some feedback about [this page](https://github.com/hazelcast/hz-docs/edit/main/docs/modules/maintain-cluster/pages/member-attributes.adoc)

Wrong variable names used (second line looks like is should be `fourCore.setAttribute()` ):
```
MemberAttributeConfig fourCore = new MemberAttributeConfig();
memberAttributeConfig.setAttribute( "CPU_CORE_COUNT", "4" );
```

This section suggests using a method ( `[HazelcastInstance](https://docs.hazelcast.org/docs/5.5.0/javadoc/com/hazelcast/core/HazelcastInstance.html).setAttribute()` ) which does not exist.
```
HazelcastInstance member4 = Hazelcast.newHazelcastInstance();
// We can also set member attributes at runtime.
member4.setAttribute( "CPU_CORE_COUNT", "2" );
```

Open docs/modules/maintain-cluster/pages/member-attributes.adoc and review the member-attributes examples identified in the issue. Check the variable names and the HazelcastInstance API reference, then update the snippets so they use valid names and methods; the issue is done when both examples are accurate.

Written by the indexing model from the issue text.