False positive word detection attached in text-only mode

Using the plain-text format when replying to an email that had the word attachment in its body, the missing attachment in the email is reported by mistake

Steps to reproduce:

• select the plain-text mail composition format
• send an email containing the word attached in the body of the message
• reply to the email without adding anything else

Expected behaviour:

• the email is sent without any notice of missing attachment

Actual behaviour:

• the notice of missing attachment appears

(Ticket Ref: #110504)