fix(core): remove unreachable and bug-prone null guards in Attribute.equals

[Alwaysgaurav1]

What changes were proposed in this PR?

In Attribute.java (common/workflow-core/src/main/scala/org/apache/texera/amber/core/tuple/Attribute.java), Attribute.equals() contained two unreachable null guards:

if (this.attributeName == null) {
    return that.attributeName == null;
}
if (this.attributeType == null) {
    return that.attributeType == null; // ignores attribute name comparison!
}

[github-actions]

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[github-actions]

👋 Thanks for opening this pull request, @Alwaysgaurav1!

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[github-actions]

Backport auto-label report

This fix: PR was checked against each actively-supported release branch. release/* labels drive the post-merge backport, so add or remove one to change where this fix lands.

Release branch	Analysis
⚠️ release/v1.3	Not labeled automatically — none of the files this PR modifies exist on this branch (common/workflow-core/src/main/scala/org/apache/texera/amber/core/tuple/Attribute.java). The fix may target code that isn't on this release, or the files were moved/renamed after the branch was cut. Please check and add release/v1.3 by hand if this fix should be backported here.
✅ release/v1.2	Change detected on this branch — label added; this fix is queued to backport here. Requested review from @xuang7.

Auto-label run.

[github-actions]

Automated Reviewer Suggestions

Based on the git blame history of the changed files, we recommend the following reviewers:

• Contributors with relevant context: @carloea2
  You can notify them by mentioning @carloea2 in a comment.