MINOR: [C++] Fix C++ Format (#55353)

### Rationale for this change
Lint C++ format fail on main

### What changes are included in this PR?
Minor lint C++ format fix

### Are these changes tested?
yes
### Are there any user-facing changes?
no

### Was AI used for this PR?

**PR code and description written by:**

- [X] Human

**Reviewed before submission by:**

- [X] Human

Authored-by: Tadeja Kadunc <tadeja.kadunc@gmail.com>
Signed-off-by: Rok Mihevc <rok@mihevc.org>

Author: tadeja

cpp/src/arrow/util/bit_util.h

@@ -168,9 +168,7 @@ constexpr bool HasSingleBit(T x) noexcept {
 }
 
 // Returns ceil(log2(x)).
-static inline int Log2(uint64_t x) {
-  return BitWidth(x - 1);
-}
+static inline int Log2(uint64_t x) { return BitWidth(x - 1); }
 
 //
 // Utilities for reading and writing individual bits by their index