Correct schema nullability declaration in tests

[alamb]

Which issue does this PR close?

Part of #2778

Rationale for this change

apache/arrow-rs#1888 (added in arrow 17.0.0) added validation to RecordBatch if the schema's declared nullability is different than its actual nullability it throws a runtime error.

What changes are included in this PR?

Correct declared schema nullability in DataFusion tests .

There are no tests in this PR -- they are covered in #2778

Are there any user-facing changes?

No, it is a test only change

[alamb]

This is a pretty easy to understand example of the issue -- prior to this PR, the fields "a" and "b" are declared as "nullable=false" but then 5 lines lower NULL data is inserted 🤦

        let batch = RecordBatch::try_new(
            Arc::clone(&schema),
            vec![
                Arc::new(Int32Array::from(vec![Some(1), Some(2), None])),
                Arc::new(Int32Array::from(vec![Some(4), None, Some(6)])),
            ],
        )?;

Now that RecordBatch::try_new validates the nullability, the schema must match the data otherwise an error results

[codecov-commenter]

Codecov Report

Merging #2802 (b6e898c) into master (533e2b4) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head b6e898c differs from pull request most recent head 5dc0e51. Consider uploading reports for the commit 5dc0e51 to get more accurate results

@@            Coverage Diff             @@
##           master    #2802      +/-   ##
==========================================
- Coverage   85.11%   85.11%   -0.01%     
==========================================
  Files         273      273              
  Lines       48240    48240              
==========================================
- Hits        41060    41059       -1     
- Misses       7180     7181       +1     

Impacted Files	Coverage Δ
...fusion/physical-expr/src/aggregate/sum_distinct.rs	92.66% <ø> (ø)
datafusion/physical-expr/src/expressions/cast.rs	98.00% <ø> (ø)
datafusion/physical-expr/src/expressions/mod.rs	100.00% <ø> (ø)
...tafusion/physical-expr/src/expressions/try_cast.rs	98.75% <ø> (ø)
datafusion/core/src/datasource/listing/helpers.rs	95.30% <100.00%> (ø)
...ore/src/physical_optimizer/aggregate_statistics.rs	100.00% <100.00%> (ø)
datafusion/core/src/physical_plan/hash_join.rs	94.68% <100.00%> (ø)
datafusion/core/src/physical_plan/memory.rs	96.03% <100.00%> (ø)
...afusion/physical-expr/src/aggregate/correlation.rs	97.97% <100.00%> (ø)
...tafusion/physical-expr/src/aggregate/covariance.rs	98.71% <100.00%> (ø)
... and 7 more

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