chore(deps): update dependency zlib to v1.3.1.bcr.6 (googleapis#15175)

Co-authored-by: Yao Cui <cuiyao@google.com>

Author: renovate-bot

MODULE.bazel

@@ -40,7 +40,7 @@ bazel_dep(name = "yaml-cpp", version = "0.8.0", dev_dependency = True, repo_name
 bazel_dep(name = "pugixml", version = "1.15", dev_dependency = True, repo_name = "com_github_zeux_pugixml")
 
 # Our `curl.BUILD` file uses these.
-bazel_dep(name = "zlib", version = "1.3.1.bcr.5")
+bazel_dep(name = "zlib", version = "1.3.1.bcr.6")
 bazel_dep(name = "c-ares", version = "1.19.1.bcr.1", repo_name = "com_github_cares_cares")
 
 # Pin this to fix a break in bazel/deps-cache.py