Many languages distinguish between inclusive and exclusive first-person plural pronouns (“we”). (Click or tap here to see more details)
The inclusive “we” specifically includes the addressee (“you and I and possibly others”), while the exclusive “we” specifically excludes the addressee (“he/she/they and I, but not you”). This grammatical distinction is called “clusivity.” While Semitic languages such as Hebrew or most Indo-European languages such as Greek or English do not make that distinction, translators of languages with that distinction have to make a choice every time they encounter “we” or a form thereof (in English: “we,” “our,” or “us”).
For this verse, translators typically select the exclusive form (excluding the readers of the letter).
Source: Velma Pickett and Florence Cowan in Notes on Translation January 1962, p. 1ff.
Note that many Common Language translations (the German Gute Nachricht Bibel, the Dutch Bijbel in Gewone Taal, the English Good News Translation, the French Bible en français courant, the Brazilian Portuguese Nova Tradução na Linguagem de Hoje, the Indonesian Alkitab dalam Bahasa Indonesia Masa Kini, or the Spanish Dios habla hoy) use the singular first personal pronoun (“I”) rather than the plural form (“we”). (Source: Paul Ellingworth in The Bible Translator 2005. p. 226ff. )