Revert "add fromChar" (#20336)

Revert "add `fromChar` (#20332)"

This reverts commit 846cc746a2.

lib/pure/strutils.nim

@@ -997,15 +997,6 @@ func toOctal*(c: char): string {.rtl, extern: "nsuToOctal".} =
     result[i] = chr(val mod 8 + ord('0'))
     val = val div 8
 
-func fromChar[T: SomeInteger](ch: char): T =
-  runnableExamples:
-    assert fromChar[int8]('6') == 6
-    doAssertRaises AssertionDefect:
-      fromChar[int8]('a')
-
-  assert isDigit(ch)
-  T(ord(ch) - ord('0'))
-
 func fromBin*[T: SomeInteger](s: string): T =
   ## Parses a binary integer value from a string `s`.
   ##