[COMMITTED] a68: fix brackets parser diagnostics

[Andreas Schwab]

../../gcc/algol68/a68-parser-brackets.cc:54:56: error: unknown conversion type character '<' in format [-Werror=format=]
   54 |   if (snprintf (buf, SNPRINTF_SIZE, "missing matching %<%s%>",
      |                                                        ^
../../gcc/algol68/a68-parser-brackets.cc:54:60: error: unknown conversion type character '>' in format [-Werror=format=]
   54 |   if (snprintf (buf, SNPRINTF_SIZE, "missing matching %<%s%>",
      |                                                            ^
cc1plus: all warnings being treated as errors
make[3]: *** [Makefile:1217: algol68/a68-parser-brackets.o] Error 1

-- 
Andreas Schwab, schwab@linux-m68k.org
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