ARROW-11586: [Rust][Datafusion] Remove force unwrap

[marcprux]

Fix for https://issues.apache.org/jira/browse/ARROW-11586

[github-actions]

https://issues.apache.org/jira/browse/ARROW-11586

[codecov-io]

Codecov Report

Merging #9479 (ed800b7) into master (5e3fcfa) will decrease coverage by 0.01%.
The diff coverage is 88.57%.

@@ Coverage Diff @@## master #9479 +/- ##
==========================================
- Coverage 82.32% 82.31% -0.02% 
==========================================
Files 233 234 +1 Lines 54446 54461 +15 ==========================================
+ Hits 44823 44828 +5 - Misses 9623 9633 +10 

Impacted Files	Coverage Δ
rust/arrow/src/array/builder.rs	84.93% <ø> (ø)
rust/arrow/src/compute/kernels/sort.rs	93.56% <ø> (ø)
rust/arrow/src/compute/kernels/substring.rs	98.29% <ø> (ø)
rust/arrow/src/compute/util.rs	98.92% <ø> (ø)
rust/arrow/src/json/reader.rs	82.82% <ø> (ø)
rust/benchmarks/src/bin/tpch.rs	38.33% <0.00%> (+0.18%)	⬆️
rust/datafusion/src/datasource/memory.rs	80.00% <ø> (ø)
rust/datafusion/src/logical_plan/dfschema.rs	85.52% <ø> (ø)
...tafusion/src/physical_plan/datetime_expressions.rs	93.28% <ø> (+0.24%)	⬆️
...atafusion/src/physical_plan/expressions/in_list.rs	75.37% <ø> (ø)
... and 41 more

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[jorgecarleitao]

I know it is draft, but it looks good to me already :)

[marcprux]

I've un-drafted it.

[Dandandan]

LGTM 👍 😎

[alamb]

Thanks @marcprux