Add comment regarding reasoning for RE2 version

Author: thisisnic

cpp/thirdparty/versions.txt

@@ -99,6 +99,9 @@ ARROW_PROTOBUF_BUILD_SHA256_CHECKSUM=2f723218f6cb709ae4cdc4fb5ed56a5951fc5d466f0
 # warnings.
 ARROW_RAPIDJSON_BUILD_VERSION=232389d4f1012dddec4ef84861face2d2ba85709
 ARROW_RAPIDJSON_BUILD_SHA256_CHECKSUM=b9290a9a6d444c8e049bd589ab804e0ccf2b05dc5984a19ed5ae75d090064806
+# RE2 2023-03-01 is pinned to avoid Abseil dependency. Versions after 2023-06-01
+# require Abseil, which would add significant build time and complexity, particularly
+# for CRAN builds. This version includes musl libc support (GH-48010).
 ARROW_RE2_BUILD_VERSION=2023-03-01
 ARROW_RE2_BUILD_SHA256_CHECKSUM=7a9a4824958586980926a300b4717202485c4b4115ac031822e29aa4ef207e48
 ARROW_SNAPPY_BUILD_VERSION=1.2.2