[class.derived.general] Revert renaming of grammar production

P2662R3 "Pack Indexing" proposed to rename the grammar production
"class-or-decltyp" to "class-or-computed-type-specifier", without
making matching changes elsewhere in the text.

Since that change would break the existing wording and does not
otherwise seem to have an beneficial effects, we are reverting it for
the moment and await clarification.

Author: tkoeppe

source/classes.tex

@@ -3403,16 +3403,16 @@
 
 \begin{bnf}
 \nontermdef{base-specifier}\br
-    \opt{attribute-specifier-seq} class-or-computed-type-specifier\br
-    \opt{attribute-specifier-seq} \keyword{virtual} \opt{access-specifier} class-or-computed-type-specifier\br
-    \opt{attribute-specifier-seq} access-specifier \opt{\keyword{virtual}} class-or-computed-type-specifier
+    \opt{attribute-specifier-seq} class-or-decltype\br
+    \opt{attribute-specifier-seq} \keyword{virtual} \opt{access-specifier} class-or-decltype\br
+    \opt{attribute-specifier-seq} access-specifier \opt{\keyword{virtual}} class-or-decltype
 \end{bnf}
 
 \begin{bnf}
-\nontermdef{class-or-computed-type-specifier}\br
+\nontermdef{class-or-decltype}\br
     \opt{nested-name-specifier} type-name\br
     nested-name-specifier \keyword{template} simple-template-id\br
-    computed-type-specifier
+    decltype-specifier
 \end{bnf}
 
 \indextext{specifier access|see{access specifier}}%