Documentation fixes from code review

Author: Alexander-Kita

website/docs/d/pi_virtual_serial_number.html.markdown

@@ -17,7 +17,7 @@ data "ibm_pi_virtual_serial_number" "ds_virtual_serial_number" {
 }
 ```
 
-**Notes**
+### Notes
 - Please find [supported Regions](https://cloud.ibm.com/apidocs/power-cloud#endpoint) for endpoints.
 - If a Power cloud instance is provisioned at `lon04`, The provider level attributes should be as follows:
   - `region` - `lon`

website/docs/d/pi_virtual_serial_numbers.html.markdown

@@ -17,7 +17,7 @@ data "ibm_pi_virtual_serial_numbers" "ds_virtual_serial_number" {
 }
 ```
 
-**Notes**
+### Notes
 - Please find [supported Regions](https://cloud.ibm.com/apidocs/power-cloud#endpoint) for endpoints.
 - If a Power cloud instance is provisioned at `lon04`, The provider level attributes should be as follows:
   - `region` - `lon`

website/docs/r/pi_virtual_serial_number.html.markdown

@@ -21,11 +21,11 @@ resource "ibm_pi_virtual_serial_number" "testacc_virtual_serial_number" {
 }
 ```
 
-**Note**
-* Please find [supported Regions](https://cloud.ibm.com/apidocs/power-cloud#endpoint) for endpoints.
-* If a Power cloud instance is provisioned at `lon04`, The provider level attributes should be as follows:
-  * `region` - `lon`
-  * `zone` - `lon04`
+### Notes
+- Please find [supported Regions](https://cloud.ibm.com/apidocs/power-cloud#endpoint) for endpoints.
+- If a Power cloud instance is provisioned at `lon04`, The provider level attributes should be as follows:
+  - `region` - `lon`
+  - `zone` - `lon04`
 
   Example usage:
 
@@ -37,7 +37,7 @@ resource "ibm_pi_virtual_serial_number" "testacc_virtual_serial_number" {
   ```
 
 **Note**
-* This resource is used to create a virtual serial number by assigning to a power instance using 'auto-assign'. Otherwise, it can only be used to manage an existing virtual serial number.
+- This resource is used to create a virtual serial number by assigning to a power instance using 'auto-assign'. Otherwise, it can only be used to manage an existing virtual serial number.
 
 ## Timeouts