pw_string: Remove problematic test

Remove a test that attempts to trigger a negative (error) return value
for snprintf. The format strings that trigger these errors vary by
platform, and a format that returns a negative result on one platform
(Linux) may crash another (Windows).

Change-Id: I7b60bc301cd534d0e78228829ea6288687e05c43
diff --git a/pw_string/format_test.cc b/pw_string/format_test.cc
index 1c44c4e..ad7e39e 100644
--- a/pw_string/format_test.cc
+++ b/pw_string/format_test.cc
@@ -40,24 +40,6 @@
   EXPECT_STREQ("12345", buffer);
 }
 
-TEST(Format, InvalidConversionSpecifier_ReturnsInvalidArgumentAndTerminates) {
-  char buffer[32] = {'?', '?', '?', '?', '\0'};
-
-  // Make the format string volatile to prevent the compiler from potentially
-  // checking this as a format string.
-  const char* volatile fmt = "abc %9999999999999999999999999999999999d4%s";
-
-  if (std::snprintf(buffer, sizeof(buffer), fmt, 123, "5") >= 0) {
-    // This snprintf implementation does not detect invalid format strings.
-    return;
-  }
-
-  auto result = Format(buffer, fmt, 123, "5");
-
-  EXPECT_EQ(Status::INVALID_ARGUMENT, result.status());
-  EXPECT_STREQ("", buffer);
-}
-
 TEST(Format, EmptyBuffer_ReturnsResourceExhausted) {
   auto result = Format(span<char>(), "?");