remove unused maxFreq var and get method

uhabits-android/src/main/java/org/isoron/uhabits/activities/common/views/FrequencyChart.kt

@@ -63,7 +63,6 @@ class FrequencyChart : ScrollableChart {
     private var primaryColor = 0
     private var isBackgroundTransparent = false
     private lateinit var frequency: HashMap<Timestamp, Array<Int>>
-    private var maxFreq = 0
     private var firstWeekday = Calendar.SUNDAY
 
     constructor(context: Context?) : super(context) {
@@ -83,7 +82,6 @@ class FrequencyChart : ScrollableChart {
 
     fun setFrequency(frequency: java.util.HashMap<Timestamp, Array<Int>>) {
         this.frequency = frequency
-        maxFreq = getMaxFreq(frequency)
         postInvalidate()
     }
 
@@ -92,15 +90,6 @@ class FrequencyChart : ScrollableChart {
         postInvalidate()
     }
 
-    private fun getMaxFreq(frequency: HashMap<Timestamp, Array<Int>>): Int {
-        var maxValue = 1
-        for (values in frequency.values) for (value in values) maxValue = max(
-            value,
-            maxValue
-        )
-        return maxValue
-    }
-
     fun setIsBackgroundTransparent(isBackgroundTransparent: Boolean) {
         this.isBackgroundTransparent = isBackgroundTransparent
         initColors()
@@ -296,6 +285,5 @@ class FrequencyChart : ScrollableChart {
             frequency[Timestamp(date)] = values
             date.add(Calendar.MONTH, -1)
         }
-        maxFreq = getMaxFreq(frequency)
     }
 }