fix(heatmap): replace SelectValue component with span for displaying selected value

frontend/src/components/git/ForgejoHeatmap.tsx

@@ -8,7 +8,6 @@ import {
   SelectContent,
   SelectItem,
   SelectTrigger,
-  SelectValue,
 } from "@/components/ui/select";
 
 interface ForgejoHeatmapProps {
@@ -150,7 +149,7 @@ function RangeSelect({
               }
         }
       >
-        <SelectValue />
+        <span>{value}</span>
       </SelectTrigger>
       <SelectContent align="end" className="min-w-[8rem]">
         {RANGE_LABELS.map((range) => (