GH-5054: CGIHTTPRequestHandler.run_cgi() HTTP_ACCEPT improperly parsed (#23638)

diff --git a/Lib/http/server.py b/Lib/http/server.py
index c611381..94f730e 100644
--- a/Lib/http/server.py
+++ b/Lib/http/server.py
@@ -1122,12 +1122,7 @@ def run_cgi(self):
         referer = self.headers.get('referer')
         if referer:
             env['HTTP_REFERER'] = referer
-        accept = []
-        for line in self.headers.getallmatchingheaders('accept'):
-            if line[:1] in "\t\n\r ":
-                accept.append(line.strip())
-            else:
-                accept = accept + line[7:].split(',')
+        accept = self.headers.get_all('accept', ())
         env['HTTP_ACCEPT'] = ','.join(accept)
         ua = self.headers.get('user-agent')
         if ua: