fix: docs: 100-model.mdx: fix deprecated .name

Author: jlecordier

content/200-orm/200-prisma-client/300-client-extensions/100-model.mdx

@@ -148,8 +148,8 @@ For example:
 // `context` refers to the current model
 const context = Prisma.getExtensionContext(this)
 
-// `context.name` returns the name of the current model
-console.log(context.name)
+// `context.$name` returns the name of the current model
+console.log(context.$name)
 
 // Usage
 await(context as any).findFirst({ args })