Avoid warnings in tests when compiling without default features

[alamb]

When testing with

cargo test -p datafusion --no-default-features -- pruning

I get this warning:

warning: unused import: `ListArray`
--> datafusion/src/physical_plan/functions.rs:1278:25
|
1278 | Int32Array, ListArray, StringArray, UInt32Array, UInt64Array,
| ^^^^^^^^^
|
= note: `#[warn(unused_imports)]` on by default

Because the test that uses it is not being compiled without the default features.

Thus move the use to the tests that need them.

[codecov-commenter]

Codecov Report

Merging #489 (ef38b41) into master (33ff660) will not change coverage.
The diff coverage is n/a.

@@ Coverage Diff @@## master #489 +/- ##
=======================================
Coverage 75.80% 75.80% =======================================
Files 153 153 Lines 25924 25924 =======================================
Hits 19652 19652 Misses 6272 6272 

Impacted Files	Coverage Δ
datafusion/src/physical_plan/functions.rs	92.70% <ø> (ø)

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