docs: Fix Getting Started Title

There's already a title at the top, so the H1 header is unneeded.

Signed-off-by: Charlie Le <[email protected]>

docs/getting-started/_index.md

@@ -6,8 +6,6 @@ no_section_index_title: true
 slug: "getting-started"
 ---
 
-# Getting Started with Cortex
-
 Cortex is a powerful platform software that can be run in two modes: as a single binary or as multiple
 independent [microservices](../architecture.md).
 This guide will help you get started with Cortex in single-binary mode using