[gcc r16-4032] libstdc++: Remove leftover __formatter_chrono base classes.

[Tomasz Kaminski]

https://gcc.gnu.org/g:c61535ff3d6dc5af775658ba50d2b870f18cf588

commit r16-4032-gc61535ff3d6dc5af775658ba50d2b870f18cf588
Author: Tomasz Kamiński <tkaminsk@redhat.com>
Date:   Tue Sep 23 07:51:18 2025 +0200

    libstdc++: Remove leftover __formatter_chrono base classes.
    
    This patch removes the __formatter_chrono<_CharT> base class from the
    formatters for utc_time, gps_time, and tai_time. These formatters
    are using the __formatter_duration<_CharT> member only.
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/chrono_io.h (formatter<chrono::utc_time, _CharT>):
            (formatter<chrono::gps_time<_Duration>, _CharT>)
            (formatter<chrono::tai_time<_Duration>, _CharT): Remove
            __formatter_chrono base class.
    
    Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
    Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>

Diff:
---
 libstdc++-v3/include/bits/chrono_io.h | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/libstdc++-v3/include/bits/chrono_io.h b/libstdc++-v3/include/bits/chrono_io.h
index ff7e8cfe6b9f..85b2013cf704 100644
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -2958,7 +2958,6 @@ namespace __format
 
   template<typename _Duration, __format::__char _CharT>
     struct formatter<chrono::utc_time<_Duration>, _CharT>
-    : __format::__formatter_chrono<_CharT>
     {
       constexpr typename basic_format_parse_context<_CharT>::iterator
       parse(basic_format_parse_context<_CharT>& __pc)
@@ -3003,7 +3002,6 @@ namespace __format
 
   template<typename _Duration, __format::__char _CharT>
     struct formatter<chrono::tai_time<_Duration>, _CharT>
-    : __format::__formatter_chrono<_CharT>
     {
       constexpr typename basic_format_parse_context<_CharT>::iterator
       parse(basic_format_parse_context<_CharT>& __pc)
@@ -3039,7 +3037,6 @@ namespace __format
 
   template<typename _Duration, __format::__char _CharT>
     struct formatter<chrono::gps_time<_Duration>, _CharT>
-    : __format::__formatter_chrono<_CharT>
     {
       constexpr typename basic_format_parse_context<_CharT>::iterator
       parse(basic_format_parse_context<_CharT>& __pc)