build: require boost >= 1.71.0

Refs: #5276
Change-Id: Ib62b24b041e21b2c017cd9c290f7d5dc09003d63
diff --git a/tests/test-case.t.cpp.sample b/tests/test-case.t.cpp.sample
index a2f74c1..07e4d2b 100644
--- a/tests/test-case.t.cpp.sample
+++ b/tests/test-case.t.cpp.sample
@@ -41,7 +41,7 @@
   int i = 0;
 
   // For reference of available Boost.Test macros, see
-  // https://www.boost.org/doc/libs/1_65_1/libs/test/doc/html/boost_test/testing_tools/summary.html
+  // https://www.boost.org/doc/libs/1_71_0/libs/test/doc/html/boost_test/testing_tools/summary.html
 
   BOOST_REQUIRE_NO_THROW(i = 1);
   BOOST_CHECK_EQUAL(i, 1);