Updating RTF Magic number to match https://www.iana.org/assignments/media-types/application/rtf

[zdiff]

Updating RTF Magic number to match the following references:

• https://www.iana.org/assignments/media-types/application/rtf
• https://github.com/file/file/blob/99d21e9f799e415ea8f616b9de093b4e9a1bae56/magic/Magdir/rtf#L11C1-L11C10
• https://www.loc.gov/preservation/digital/formats/fdd/fdd000473.shtml

It appears as though the version number is not required in a Rich Text Format header to create a readable rtf file.

However, these magic numbers seem to diverge from the official specification from Microsoft, that indicate a version number is required:

An entire RTF file is considered a group and must be enclosed in braces. The control word \rtf<N> must follow the opening brace. The numeric parameter <N> identifies the version of the RTF standard used. The RTF standard described in this RTF Specification, although titled as version 1.{0, 1, 2, 3, 4, 5, 6, 7, 8, 9.1}, continues to correspond syntactically to RTF Specification version 1. Therefore, the numeric parameter <N> for the \rtf control word should still be emitted as 1.
sources:

• https://msopenspecs.azureedge.net/files/Archive_References/[MSFT-RTF].pdf
• https://latex2rtf.sourceforge.net/rtfspec_6.html#rtfspec_7

This PR increases the detection of Rich Text Format files that do not include a version number

[gabriel-vasile]

Thank you!