build: fix incorrect g++ warning message

The warning message was inadvertently changed to a newer version of
g++ than the one being checked for when a refactor PR was merged to
v18.x-staging.

Refs: #47667
PR-URL: #51695
Reviewed-By: Ruy Adorno <ruyadorno@google.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>

configure.py

@@ -1057,7 +1057,7 @@ def check_compiler(o):
   if not ok:
     warn(f'failed to autodetect C++ compiler version (CXX={CXX})')
   elif clang_version < (8, 0, 0) if is_clang else gcc_version < (8, 3, 0):
-    warn(f'C++ compiler (CXX={CXX}, {version_str}) too old, need g++ 10.1.0 or clang++ 8.0.0')
+    warn(f'C++ compiler (CXX={CXX}, {version_str}) too old, need g++ 8.3.0 or clang++ 8.0.0')
 
   ok, is_clang, clang_version, gcc_version = try_check_compiler(CC, 'c')
   version_str = ".".join(map(str, clang_version if is_clang else gcc_version))