Reduce the TransportSpeedReduction stat of the Fire Beetle (FAForev…

…er#6469)

## Description of the proposed changes
Unlike other Tech 2 units, the Fire Beetle only takes up one clamp on
transports. This makes it possible to load the same quantities of Fire
Beetles and Tech 1 units into transports. To ensure that the Fire Beetle
does not slow transports down excessively, its `TransportSpeedReduction`
stat is reduced to match that of Tech 1 units.

**Fire Beetle: T2 Mobile Bomb (XRL0302):**
   - TransportSpeedReduction: 0.3 --> 0.15

## Checklist
- [x] Changes are documented in the changelog for the next game version

changelog/snippets/balance.6469.md

@@ -0,0 +1,4 @@
+- (#6469) Unlike other Tech 2 units, the Fire Beetle only takes up one clamp on transports. This makes it possible to load the same quantities of Fire Beetles and Tech 1 units into transports. To ensure that the Fire Beetle does not slow transports down excessively, its `TransportSpeedReduction` stat is reduced to match that of Tech 1 units.
+
+  - Fire Beetle: T2 Mobile Bomb (XRL0302):
+    - TransportSpeedReduction: 0.3 --> 0.15

units/XRL0302/XRL0302_unit.bp

@@ -139,6 +139,7 @@ UnitBlueprint{
         MeshExtentsY = 0.25,
         MeshExtentsZ = 0.65,
         MotionType = "RULEUMT_Land",
+        TransportSpeedReduction = 0.15,
         TurnRadius = 4,
         TurnRate = 200,
     },