Remove unreachable 'declarations' grammar production (#188)

Fixes: #187

Author: amartini51

TSPL.docc/ReferenceManual/Declarations.md

@@ -34,7 +34,6 @@ the term *declaration* covers both declarations and definitions.
 > *declaration* → *macro-declaration* \
 > *declaration* → *operator-declaration* \
 > *declaration* → *precedence-group-declaration* \
-> *declarations* → *declaration* *declarations*_?_
 
 ## Top-Level Code
 
@@ -1828,21 +1827,6 @@ as described in <doc:Patterns#Enumeration-Case-Pattern>.
   and they behave differently.
 -->
 
-<!--
-  old-grammar
-  Grammar of an enumeration declaration
-
-  enum-declaration -> attribute-list-OPT ``enum`` enum-name generic-parameter-clause-OPT type-inheritance-clause-OPT enum-body
-  enum-name -> identifier
-  enum-body -> ``{`` declarations-OPT ``}``
-
-  enum-member-declaration -> attribute-list-OPT ``case`` enumerator-list
-  enumerator-list -> enumerator raw-value-assignment-OPT | enumerator raw-value-assignment-OPT ``,`` enumerator-list
-  enumerator -> enumerator-name tuple-type-OPT
-  enumerator-name -> identifier
-  raw-value-assignment -> ``=`` literal
--->
-
 ## Structure Declaration
 
 A *structure declaration* introduces a named structure type into your program.

TSPL.docc/ReferenceManual/SummaryOfTheGrammar.md

@@ -748,7 +748,6 @@ make the same change here also.
 > *declaration* → *subscript-declaration* \
 > *declaration* → *operator-declaration* \
 > *declaration* → *precedence-group-declaration* \
-> *declarations* → *declaration* *declarations*_?_
 
 > Grammar of a top-level declaration:
 >