Clarify the "RecordNotFound" exception in update() and delete()

[jyasskin]

At

docs/content/200-orm/500-reference/050-prisma-client-reference.mdx

Line 906 in bf3fd9b

| `RecordNotFound` exception | | Exception is thrown if record does not exist. |

and

docs/content/200-orm/500-reference/050-prisma-client-reference.mdx

Line 1161 in bf3fd9b

| `RecordNotFound` exception | | Throws an exception if record does not exist. |

there's no Prisma.RecordNotFound exception type. I think those should refer to the "P2025" error code in Prisma.PrismaClientKnownRequestError.