MINOR: [C++] Make clang-tidy stop complaining about C arrays (apache#36102)

### Rationale for this change

`std::array` is rarely a good fit for the kind of low-level array and buffer manipulation that Arrow does, so having `clang-tidy` complaining about C-style arrays confuses more than it helps.

### What changes are included in this PR?

Change in `.clang-tidy`.

### Are these changes tested?

I checked on my editor. Warnings not shown anymore.

Authored-by: Felipe Oliveira Carvalho <[email protected]>
Signed-off-by: Antoine Pitrou <[email protected]>

Author: felipecrv

.clang-tidy

@@ -21,6 +21,7 @@ Checks: |
   -clang-analyzer-alpha*,
   google-*,
   modernize-*,
+  -modernize-avoid-c-arrays,
   -modernize-use-trailing-return-type,
   -modernize-use-nodiscard,
 # produce HeaderFilterRegex from cpp/build-support/lint_exclusions.txt with: