Update requirements wording

I'm adding some wording to our hardware requirements to explain that needs vary
by workload. I also included some examples of factors that may influence the
workload.

doc/administration/high_availability/README.md

@@ -172,6 +172,8 @@ environment that supports about 10,000 users. The specifications below are a
 representation of the work so far. The specifications may be adjusted in the
 future based on additional testing and iteration.
 
+NOTE: **Note:** The specifications here were performance tested against a specific coded workload. Your exact needs may be more, depending on your workload. Your workload is influenced by factors such as - but not limited to - how active your users are, how much automation you use, mirroring, and repo/change size.
+
 - 3 PostgreSQL - 4 CPU, 16GiB memory per node
 - 1 PgBouncer - 2 CPU, 4GiB memory
 - 2 Redis - 2 CPU, 8GiB memory per node

doc/install/requirements.md

@@ -62,6 +62,8 @@ NOTE: **Note:** Since file system performance may affect GitLab's overall perfor
 
 ### CPU
 
+This is the recommended minimum hardware for a handful of example GitLab user base sizes. Your exact needs may be more, depending on your workload. Your workload is influenced by factors such as - but not limited to - how active your users are, how much automation you use, mirroring, and repo/change size.
+
 - 1 core supports up to 100 users but the application can be a bit slower due to having all workers and background jobs running on the same core
 - **2 cores** is the **recommended** minimum number of cores and supports up to 100 users
 - 4 cores supports up to 500 users
@@ -71,6 +73,8 @@ NOTE: **Note:** Since file system performance may affect GitLab's overall perfor
 
 ### Memory
 
+This is the recommended minimum hardware for a handful of example GitLab user base sizes. Your exact needs may be more, depending on your workload. Your workload is influenced by factors such as - but not limited to - how active your users are, how much automation you use, mirroring, and repo/change size.
+
 You need at least 8GB of addressable memory (RAM + swap) to install and use GitLab!
 The operating system and any other running applications will also be using memory
 so keep in mind that you need at least 4GB available before running GitLab. With