fix(state): only apply ifdef on Unity 2019.2 or newer

The ENABLE_LEGACY_INPUT_MANAGER was only added in Unity 2019.2 so
any version before that won't understand the ifdef and therefore
just output the debug warning.

This fix wraps that whole block in a check to see if Unity 2019.2
or newer is being used, if its not then it just does the default
process and if the user is using the new Input System but has this
package installed then they won't get any debug warnings, but as this
is based on such an old version of unity then this is acceptable.

Author: thestonefox

Runtime/SharedResources/Scripts/UnityInputManagerAxis1DAction.cs

@@ -47,10 +47,14 @@ public float Multiplier
         /// <inheritdoc />
         public void Process()
         {
+#if UNITY_2019_2_OR_NEWER
 #if ENABLE_LEGACY_INPUT_MANAGER
             Receive(Input.GetAxis(AxisName) * Multiplier);
 #else
             Debug.LogWarning("The Legacy Unity Input Manager is disabled in the player settings.");
+#endif
+#else
+            Receive(Input.GetAxis(AxisName) * Multiplier);
 #endif
         }
     }

Runtime/SharedResources/Scripts/UnityInputManagerAxis2DAction.cs

@@ -81,10 +81,14 @@ public float YMultiplier
         /// <inheritdoc />
         public void Process()
         {
+#if UNITY_2019_2_OR_NEWER
 #if ENABLE_LEGACY_INPUT_MANAGER
             Receive(new Vector2(Input.GetAxis(XAxisName) * XMultiplier, Input.GetAxis(YAxisName) * YMultiplier));
 #else
             Debug.LogWarning("The Legacy Unity Input Manager is disabled in the player settings.");
+#endif
+#else
+            Receive(new Vector2(Input.GetAxis(XAxisName) * XMultiplier, Input.GetAxis(YAxisName) * YMultiplier));
 #endif
         }
     }

Runtime/SharedResources/Scripts/UnityInputManagerButtonAction.cs

@@ -30,10 +30,14 @@ public KeyCode KeyCode
         /// <inheritdoc />
         public void Process()
         {
+#if UNITY_2019_2_OR_NEWER
 #if ENABLE_LEGACY_INPUT_MANAGER
             Receive(Input.GetKey(KeyCode));
 #else
             Debug.LogWarning("The Legacy Unity Input Manager is disabled in the player settings.");
+#endif
+#else
+            Receive(Input.GetKey(KeyCode));
 #endif
         }
     }