Fix documentation of compbrl and comp6

[bertfrees]

From the current documentation it seems like there are two computer braille modes, one for 6-dot and one for 8-dot, but that is not the case. There is only one computer braille mode.

compbrl characters

If the characters are found within a block of text surrounded by whitespace the entire block is translated according to the default braille representations defined by the Character-Definition Opcodes, if 8-dot computer braille is enabled or according to the dot patterns given in the comp6 opcode (see comp6), if 6-dot computer braille is enabled. For example:

compbrl www translate URLs in computer braille

comp6 character dots

This opcode specifies the translation of characters in 6-dot computer braille. The first operand must be a single character. The second operand may specify as many cells as necessary. The opcode is somewhat of a misnomer, since any dots, not just dots 1 through 6, can be specified. This even includes virtual dots (see virtual dots).