That bit is not for Catholics
Ausfag, Catholic in laws, they never say that in mass.
I always thought Henry VIII added the doxology to the end of the Catholic Lord's Prayer
Lord's Prayer doxology
Another familiar doxology is the one often added at the end of the Lord's Prayer: "For thine is the kingdom, and the power, and the glory, forever and ever, Amen." This is found in manuscripts representative of the Byzantine text of Matthew 6:13, but not in the manuscripts considered by Catholics to be the most reliable. According to Scrivener's "Supplement to the Authorized English version of New Testament", it is omitted by eight out of 500 or so manuscripts. Some scholars do not consider it part of the original text of Matthew, and modern translations do not include it, mentioning it only in footnotes. The same doxology, in the form "For the kingdom, the power, and the glory are yours, now and for ever", is used in the Roman Rite of the Mass, after the Embolism, introduced in 1970. The Catholic Encyclopedia (1914) claims that this doxology "appears in the Greek textus receptus and has been adopted in the later editions of the Book of Common Prayer, [and] is undoubtedly an interpolation." In fact, the Lord's Prayer doxology is often left away by Catholics, such as in the Liturgy of the Hours, or when, which is quite often outside Mass, a Hail Mary follows immediately (e. g. in the Rosary where the Gloria Patri serves as doxology).
https://en.wikipedia.org/wiki/Doxology