deps: stop building libcurl docs (#38172)

This should be turned off as it's not needed.
Ref Homebrew/homebrew-core#205269

Fix #37470

Signed-off-by: Takeshi Yoneda <[email protected]>
Signed-off-by: Ryan Northey <[email protected]>

Author: mathetake

bazel/foreign_cc/BUILD

@@ -266,6 +266,7 @@ envoy_cmake(
     cache_entries = {
         "BUILD_CURL_EXE": "off",
         "BUILD_TESTING": "off",
+        "BUILD_LIBCURL_DOCS": "off",
         "BUILD_SHARED_LIBS": "off",
         "CURL_HIDDEN_SYMBOLS": "off",
         "CURL_USE_LIBSSH2": "off",