Drop eslint-plugin-rxjs-angular

The plugin has not been update for more than one year and it does not support ESLint 9.
Eslint-config-angular only used one rule (rxjs-angular/prefer-async-pipe), so keeping the plugin does not worth the effort.

Author: amikheychik

src/index.ts

@@ -23,7 +23,6 @@ export = {
             extends: [
                 './rules/eslint-config',
                 './rules/angular',
-                './rules/rxjs-angular',
             ],
         },
         {

src/rules/index.adoc

@@ -3,5 +3,3 @@
 include::eslint-config/index.adoc[leveloffset=+1]
 
 include::angular/index.adoc[leveloffset=+1]
-
-include::rxjs-angular/index.adoc[leveloffset=+1]