docs: Fix typo in theming example (#22765)
docs: Fix typo in theming example (#22765)


josephperrott/material2,crisbeto/material2,crisbeto/material2,josephperrott/material2,angular/components,angular/components,DevVersion/material2,DevVersion/material2,mmalerba/material2,josephperrott/material2,mmalerba/material2,DevVersion/material2,josephperrott/material2,mmalerba/material2,angular/components,mmalerba/material2,DevVersion/material2,josephperrott/material2,mmalerba/material2,DevVersion/material2,angular/components,crisbeto/material2,crisbeto/material2