glslang: fix compilation on certain newer compilers

This is already fixed in the latest glslang source code, but updating may be too risky for love 11.x.

src/libraries/glslang/glslang/Include/PoolAlloc.h

@@ -304,7 +304,6 @@ public:
     size_type max_size() const { return static_cast<size_type>(-1) / sizeof(T); }
     size_type max_size(int size) const { return static_cast<size_type>(-1) / size; }
 
-    void setAllocator(TPoolAllocator* a) { allocator = *a; }
     TPoolAllocator& getAllocator() const { return allocator; }
 
 protected: