🔧 chore(RDSDiskSpaceLimit.md): add missing 'bash' syntax highlighting to code block

Fixes linting error in markdownlint

```
Error: content/runbooks/rds/RDSDiskSpaceLimit.md:80 MD031/blanks-around-fences Fenced code blocks should be surrounded by blank lines [Context: "```"] https://github.com/DavidAnson/markdownlint/blob/v0.34.0/doc/md031.md
Error: content/runbooks/rds/RDSDiskSpaceLimit.md:83 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"] https://github.com/DavidAnson/markdownlint/blob/v0.34.0/doc/md040.md

```

Author: Daria Lapina

content/runbooks/rds/RDSDiskSpaceLimit.md

@@ -78,9 +78,10 @@ You must avoid reaching no disk space left situation.
         ```bash
         export AWS_PROFILE=<AWS account>
         ```
+
     2. Request aws admin permissions
 
-        ```
+        ```bash
         qontoctl aws admin get-access "bump $RDS_INSTANCE storage"
         ```