rfc(0021): remove repetitive language

Author: jrentlez

rfc/0021-sheet-row-access-syntax/README.md

@@ -32,7 +32,7 @@ RFC 0020 definitions are unnecessarily complicated to users:
 
 ## Explanation
 
-This is the current way of accessing the sheet values of a table row, as
+Below is the current way of accessing the sheet values of a table row, as
 specified in RFC 0020:
 
 ```jayvee
@@ -51,12 +51,12 @@ This syntax introduced two new concepts:
 - `SheetRow` as a special value type.
 - The `[]` syntax to access the values of a sheet row.
 
-This RFC attempts to replace these new concepts with existing ones
+We replace these new concepts with existing ones.
 
 ### `Collection<text>` replaces `SheetRow`
 
 Semantically, `SheetRow` is an array of strings, which is identical to the
-already existing value type `Collection<text>`.
+existing value type `Collection<text>`.
 
 ### `.` replaces `[]`