fix(tokenizer): Remove unnecessary templates on Tiktoken impl methods

These was likely needed in the original implementation because of being
called with different types for allowed_special, but here they're only ever
used with an Encoder type so the template is unnecessary.

pytorch#1251
Branch: TokenizersCpp-1251

Signed-off-by: Gabe Goodhart <ghart@us.ibm.com>

tokenizer/tiktoken.cpp

@@ -242,11 +242,10 @@ static std::vector<uint64_t> _byte_pair_encode(
 // ------------------------------Util end------------------------------------
 // -------------------------private method start-------------------------------
 
-template <typename T>
 std::pair<std::optional<std::string>, re2::StringPiece>
 Tiktoken::_split_with_allowed_special_token(
     re2::StringPiece& input,
-    const T& allowed_special) const {
+    const Encoder& allowed_special) const {
   if (!_special_token_regex) {
     return std::make_pair(std::nullopt, input);
   }
@@ -293,10 +292,9 @@ void Tiktoken::_encode(
   }
 }
 
-template <typename T>
 std::pair<std::vector<uint64_t>, uint64_t> Tiktoken::_encode_with_special_token(
     const std::string& text,
-    const T& allowed_special) const {
+    const Encoder& allowed_special) const {
   std::vector<uint64_t> tokens;
   uint64_t last_piece_token_len = 0;
   re2::StringPiece input(text);

tokenizer/tokenizer.h

@@ -118,21 +118,19 @@ class Tiktoken : public Tokenizer {
     return special_tokens;
   }
 
-  template <typename T>
   std::pair<std::optional<std::string>, re2::StringPiece>
   _split_with_allowed_special_token(
       re2::StringPiece& input,
-      const T& allowed_special) const;
+      const Encoder& allowed_special) const;
 
   void _encode(
       re2::StringPiece& input,
       std::vector<uint64_t>& ret,
       uint64_t& last_piece_token_len) const;
 
-  template <typename T>
   std::pair<std::vector<uint64_t>, uint64_t> _encode_with_special_token(
       const std::string& text,
-      const T& allowed_special) const;
+      const Encoder& allowed_special) const;
 
   // Removed negative lookahead \s+(?!\S) since it's not supported by RE2.
   const std::string _pattern =