apacheGH-40814: [C++] Thirdparty: bump zstd to 1.5.6 (apache#40837)

### Rationale for this change

Zstd releases 1.5.6 here: https://github.com/facebook/zstd/releases/tag/v1.5.6

### What changes are included in this PR?

Change default zstd to 1.5.6

### Are these changes tested?

Already has test

### Are there any user-facing changes?

no

* GitHub Issue: apache#40814

Authored-by: mwish <maplewish117@gmail.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>

cpp/thirdparty/versions.txt

@@ -117,8 +117,8 @@ ARROW_XSIMD_BUILD_VERSION=9.0.1
 ARROW_XSIMD_BUILD_SHA256_CHECKSUM=b1bb5f92167fd3a4f25749db0be7e61ed37e0a5d943490f3accdcd2cd2918cc0
 ARROW_ZLIB_BUILD_VERSION=1.3.1
 ARROW_ZLIB_BUILD_SHA256_CHECKSUM=9a93b2b7dfdac77ceba5a558a580e74667dd6fede4585b91eefb60f03b72df23
-ARROW_ZSTD_BUILD_VERSION=1.5.5
-ARROW_ZSTD_BUILD_SHA256_CHECKSUM=9c4396cc829cfae319a6e2615202e82aad41372073482fce286fac78646d3ee4
+ARROW_ZSTD_BUILD_VERSION=1.5.6
+ARROW_ZSTD_BUILD_SHA256_CHECKSUM=8c29e06cf42aacc1eafc4077ae2ec6c6fcb96a626157e0593d5e82a34fd403c1
 
 
 # The first field is the name of the environment variable expected by cmake.