Switch llhttp FetchContent to git repository

The tarball download redirects to codeload.github.com, which can be
unreliable in restricted network environments. Fetching the same release
via git uses github.com directly and pins the exact commit.

CMakeLists.txt

@@ -80,10 +80,9 @@ FetchContent_MakeAvailable(simdutf)
 
 FetchContent_Declare(
   llhttp
-  URL "https://github.com/nodejs/llhttp/archive/refs/tags/release/v9.2.1.tar.gz"
-  URL_HASH
-    SHA256=3c163891446e529604b590f9ad097b2e98b5ef7e4d3ddcf1cf98b62ca668f23e
-  DOWNLOAD_EXTRACT_TIMESTAMP ON)
+  GIT_REPOSITORY https://github.com/nodejs/llhttp.git
+  GIT_TAG 610a87d755f6bae466cd871c2ba97574ccac5483 # release/v9.2.1
+)
 set(BUILD_SHARED_LIBS
     OFF
     CACHE INTERNAL "")