Fix typo in doc for DKIM signature
Fix typo in doc for DKIM signature

gnat42/LexikMailerBundle,lexik/LexikMailerBundle,bendavies/LexikMailerBundle,bendavies/LexikMailerBundle,Avtonom/EmailTemplateBundle,Avtonom/EmailTemplateBundle,lexik/LexikMailerBundle,gnat42/LexikMailerBundle