remove deprecated and broken nimweb tools

[ringabout]

tools/nimweb.nim has been deprecated since b1b58b8#diff-548a3839d9ea07f9b217b687ec4810f720118846907ef7cfa9f0c04a6b1a7dff
and is broken now

C:\Users\blue\Desktop\Nim\tools\nimweb.nim(123, 41) Error: type mismatch: got <macro (e: varargs[untyped]): untyped{.noSideEffect, gcsafe, locks: <unknown>.}, string>
but expected one of:
proc `&`[T](x: T; y: seq[T]): seq[T]
  first type mismatch at position: 2
  required type for y: seq[T]
  but expression '`&`("$1-$2-$3T00:00:00Z" %
    [year, repeat("0", 2 - len(month)) & month, repeat("0", 2 - len(day)) & day],
    "</updated>")' is of type: string
6 other mismatching symbols have been suppressed; compile with --showAllMismatches:on to see them

expression: `&`(updated, `&`("$1-$2-$3T00:00:00Z" %
    [year, repeat("0", 2 - len(month)) & month, repeat("0", 2 - len(day)) & day],
                 "</updated>"))

[github-actions]

Thanks for your hard work on this PR!
The lines below are statistics of the Nim compiler built from 9561408

Hint: mm: orc; threads: on; opt: speed; options: -d:release
164199 lines; 11.407s; 668.074MiB peakmem