Fix options help text

Author: Xaeroxe

compiler/rustc_session/src/options.rs

@@ -1707,7 +1707,7 @@ options! {
  check_cfg_all_expected:bool = (false, parse_bool,[UNTRACKED],
 "show all expected values in check-cfg diagnostics (default: no)"),
  checksum_hash_algorithm:Option<SourceFileHashAlgorithm> = (None, parse_cargo_src_file_hash,[TRACKED],
-"hash algorithm of source files used to check freshness in cargo (`sha256`)"),
+"hash algorithm of source files used to check freshness in cargo (`blake3` or `sha256`)"),
  codegen_backend:Option<String> = (None, parse_opt_string,[TRACKED],
 "the backend to use"),
  combine_cgu:bool = (false, parse_bool,[TRACKED],