docs: move section on subscribing to observable (#46655)
docs: move section on subscribing to observable (#46655)

This change moves a section of the text to a more logical location in the document flow.

fixes #43235

PR Close #46655

angular-indonesia/angular,angular-indonesia/angular,angular/angular,gnomeontherun/angular,angular-indonesia/angular,angular/angular,gkalpak/angular,gnomeontherun/angular,gkalpak/angular,angular/angular,JiaLiPassion/angular,gkalpak/angular,gkalpak/angular,JiaLiPassion/angular,angular-indonesia/angular,angular/angular,JiaLiPassion/angular,JiaLiPassion/angular,gnomeontherun/angular,gnomeontherun/angular