refactoring: sine function test, rename with the tested value

src/test/test_funktionen.c

@@ -138,7 +138,7 @@ void test_howManyTimes_e_appearsIn_Beere(void)
 }
 
 
-void test_sine(void) {
+void test_sine_for_0_5(void) {
     float result = sine(0.5);
     TEST_ASSERT_EQUAL_FLOAT(0.479426, result);
 }