Update Unicode.jl (#50087)

Correct confusing typo in documentation

stdlib/Unicode/src/Unicode.jl

@@ -229,7 +229,7 @@ to perform custom normalizations, such as [`Unicode.julia_chartransform`](@ref).
 
 For example, the string `"noël"` can be constructed in two canonically equivalent ways
 in Unicode, depending on whether `"ë"` is formed from a single codepoint U+00EB or
-from the ASCII character `'o'` followed by the U+0308 combining-diaeresis character.
+from the ASCII character `'e'` followed by the U+0308 combining-diaeresis character.
 
 ```jldoctest
 julia> s1 = "no\u00EBl"