Balance the warning suppression the split separated

unit-regression2.cpp opens a DOCTEST_CLANG_SUPPRESS_WARNING_PUSH block at
the top and closed it at the very bottom, which the split moved into
unit-regression3.cpp: one file was left with a push and no pop, the other
with a pop and no push, which clang reports as an error.

Give each file the pair it needs.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

tests/src/unit-regression2.cpp

@@ -1240,3 +1240,5 @@ TEST_CASE("regression tests 2")
     }
 #endif
 }
+
+DOCTEST_CLANG_SUPPRESS_WARNING_POP

tests/src/unit-regression3.cpp

@@ -32,6 +32,10 @@ using ordered_json = nlohmann::ordered_json;
 #include <string>
 #include <vector>
 
+// NLOHMANN_JSON_SERIALIZE_ENUM uses a static std::pair
+DOCTEST_CLANG_SUPPRESS_WARNING_PUSH
+DOCTEST_CLANG_SUPPRESS_WARNING("-Wexit-time-destructors")
+
 TEST_CASE_TEMPLATE("issue #4798 - nlohmann::json::to_msgpack() encode float NaN as double", T, double, float) // NOLINT(readability-math-missing-parentheses, bugprone-throwing-static-initialization)
 {
     // With issue #4798, we encode NaN, infinity, and -infinity as float instead