Disable Unity's support for printing floating point numbers to avoid warnings

Example:
../../tests/unity/unity.c: In function ‘UnityPrintFloat’:
../../tests/unity/unity.c:271:34: warning: comparing floating point with == or != is unsafe [-Wfloat-equal]
     if (number < 0.0f || (number == 0.0f && 1.0f / number < 0.0f))
                                  ^
../../tests/unity/unity.c:278:16: warning: comparing floating point with == or != is unsafe [-Wfloat-equal]
     if (number == 0.0f) UnityPrint("0");
                ^

Fixes Gitlab issue #427

Upstream ticket filed at https://github.com/ThrowTheSwitch/Unity/issues/314