Fix build error due to const qualifiers not matching

Signed-off-by: amzn-sj <srikkant@amazon.com>

Gems/Terrain/Code/Source/TerrainSystem/TerrainSystem.cpp

@@ -253,7 +253,7 @@ AZStd::vector<AZ::Vector3> TerrainSystem::GenerateInputPositionsFromRegion(
 }
 
 AZStd::vector<AZ::Vector3> TerrainSystem::GenerateInputPositionsFromListOfVector2(
-    const AZStd::span<AZ::Vector2>& inPositionsVec2) const
+    const AZStd::span<const AZ::Vector2> inPositionsVec2) const
 {
     AZStd::vector<AZ::Vector3> inPositions;
     inPositions.reserve(inPositionsVec2.size());

Gems/Terrain/Code/Source/TerrainSystem/TerrainSystem.h

@@ -322,7 +322,7 @@ namespace Terrain
             const AZ::Aabb& inRegion,
             const AZ::Vector2& stepSize) const;
         AZStd::vector<AZ::Vector3> GenerateInputPositionsFromListOfVector2(
-            const AZStd::span<AZ::Vector2>& inPositionsVec2) const;
+            const AZStd::span<const AZ::Vector2> inPositionsVec2) const;
 
         // AZ::TickBus::Handler overrides ...
         void OnTick(float deltaTime, AZ::ScriptTimePoint time) override;