The test file of the Secret Handshake exercise executes all tests by default. (#1071)

* Secret Handshake: Revised the tests and .meta/example.c.

- The previous version of tests let solutions with extra actions pass.

- The tests now require that each solution returns an array of size 4,
and the unused slots of the array be filled with NULL.

- .meta/example.c has been revised suitably so that it passes all
revised tests.

* Secret Handshake: Reformat three C files with clang-format.

* Secret Handshake: Removed unnecessary type cast of calloc.

* Secret Handshake: Run format.sh for correcting the format of codes.

* Secret Handshake: Format fix of one more file.

* Update exercises/practice/secret-handshake/test_secret_handshake.c

Co-authored-by: Ryan Hartlage <2488333+ryanplusplus@users.noreply.github.com>

* Secret Handshake: Removed the two lines (for testing) I forgot to remove.

---------

Co-authored-by: Ryan Hartlage <2488333+ryanplusplus@users.noreply.github.com>

[no important files changed]

Author: borderite

exercises/practice/secret-handshake/test_secret_handshake.c

@@ -4,9 +4,6 @@
 
 #define ARRAY_SIZE 4
 
-#undef TEST_IGNORE
-#define TEST_IGNORE()
-
 void setUp(void)
 {
 }