Update form-validation.md missing ' in line 27

Missing closing ' in $form->dataFieldByName('MyRequiredField')
Merge pull request #3235 from nhorstmeier/patch-1

Update form-validation.md missing ' in line 27
Update advanced-templates.md

Minor spelling fix
Merge pull request #3243 from Olliepop/patch-1

Update advanced-templates.md