Drop helloworld-observ-lib as an outdated example (#1448)

Author: v-zhuravlev

README.md

@@ -41,9 +41,7 @@ The monitoring mixins in this repository use two linting tools to ensure quality
 
 Observability library is a flexible format to describe dashboards and alerts in a modular way so libraries can be imported into one another or into monitoring-mixins. Observability libraries can be found in folders with `-observ-lib` suffix. [Common library](https://github.com/grafana/jsonnet-libs/tree/master/common-lib) is also used to apply consistent style options.
 
-See [helloworld-observ-lib](helloworld-observ-lib/) for starter template and format description.
-
-More examples:
+Some examples:
  - [windows-observ-lib](windows-observ-lib/)
 
  ### Observability libraries signal extention

common-lib/README.md

@@ -32,7 +32,7 @@ local commonlib = import 'github.com/grafana/jsonnet-libs/common-lib/common/main
 local cpuPanel = oldPanel + commonlib.panels.cpu.timeSeries.utilization.stylize();
 ```
 
-See [windows-observ-lib](../windows-observ-lib/README.md) or [helloworld-observ-lib](../helloworld-observ-lib/README.md) for full example.
+See [windows-observ-lib](../windows-observ-lib/README.md) for implementation example.
 
 ### Signals