docs: standardize cross-reference link format to markdown

docs/01-rainbow-triangle.md

@@ -630,7 +630,7 @@ let shader_module = device.create_shader_module(
 
 New concept: **GPU memory isolation.** The GPU cannot read Rust heap or stack
 memory directly. Vertex data must be laid out as a flat byte array and uploaded
-into a dedicated GPU [[buffer slice]](concepts/GLOSSARY.md#buffer-slice). The
+into a dedicated GPU [buffer slice](concepts/GLOSSARY.md#buffer-slice). The
 pipeline configuration then describes how to interpret those bytes: how many
 bytes per vertex, what format each attribute has, and where in the vertex
 strides the attribute begins.