Remove Lo (other letter) surrogate pairs (#43836)

See dotnet/csharplang#1742 for details.

Author: BillWagner

docs/csharp/fundamentals/coding-style/identifier-names.md

@@ -19,7 +19,7 @@ You can declare identifiers that match C# keywords by using the `@` prefix on th
 For a complete definition of valid identifiers, see the [Identifiers article in the C# Language Specification](~/_csharpstandard/standard/lexical-structure.md#643-identifiers).
 
 > [!IMPORTANT]
-> [The C# language specification](~/_csharpstandard/standard/lexical-structure.md#643-identifiers) only allows letter (Lu, Ll, Lt, Lm, Lo or Nl), digit (Nd), connecting (Pc), combining (Mn or Mc), and formatting (Cf) categories. Anything outside that is automatically replaced using `_`. This might impact certain Unicode characters.
+> [The C# language specification](~/_csharpstandard/standard/lexical-structure.md#643-identifiers) only allows letter (Lu, Ll, Lt, Lm, or Nl), digit (Nd), connecting (Pc), combining (Mn or Mc), and formatting (Cf) categories. Anything outside that is automatically replaced using `_`. This might impact certain Unicode characters.
 
 ## Naming conventions