docs: Update arm agent types (#402)

## 📝 Description

Updated `r1-standard-4` agent type.
Added    `r1-standard-2` agent type.

Co-authored-by: Damjan Bećirović <[email protected]>

Author: bogyo210

docs/docs/reference/machine-types.md

@@ -112,7 +112,8 @@ The r1 generation is presented in the following types:
 
 | Type | Virtual CPUs | Memory (GB) | Disk (GB) |
 |--|--|--|--|
-| `r1-standard-4` | 4 | 10 | 65 |
+| `r1-standard-2` | 2 | 4 | 55 |
+| `r1-standard-4` | 4 | 8 | 65 |
 
 R1 Generation machine types can only be paired with: