LibJS: Pad the capacity of BasicBlock while growing it

Just using Vector::resize() meant that we allocated exact capacity
instead of leaving padding at the end. This patch adds a call to
grow_capacity() before resize(), which ensures that we grow with the
usual extra padding.

Userland/Libraries/LibJS/Bytecode/BasicBlock.cpp

@@ -43,6 +43,7 @@ void BasicBlock::dump(Bytecode::Executable const& executable) const
 
 void BasicBlock::grow(size_t additional_size)
 {
+    m_buffer.grow_capacity(m_buffer.size() + additional_size);
     m_buffer.resize(m_buffer.size() + additional_size);
 }