Fix minimap rendering regression

The normal map was not bound properly, so the shading based on the height map had gone missing.

client/shaders/minimap_shader/opengl_fragment.glsl

@@ -1,4 +1,5 @@
 uniform sampler2D baseTexture;
+#define normalTexture texture1
 uniform sampler2D normalTexture;
 uniform vec3 yawVec;