Clear out fix-me markers.

I've reached out to engineering about the TR markers; what's left
doesn't need to block shipping the initial version of this chapter.

Author: amartini51

TSPL.docc/LanguageGuide/Macros.md

@@ -356,7 +356,7 @@ regardless of what code comes before and after it.
 This limitation helps make macro expansion easier to understand,
 and helps your code build faster
 because Swift can avoid expanding macros that haven't changed.
-<!-- XXX TR: Confirm -->
+<!-- TODO TR: Confirm -->
 Swift helps macro authors avoid accidentally reading other input
 by restricting the code that implements macros:
 

TSPL.docc/ReferenceManual/Attributes.md

@@ -35,13 +35,8 @@ The arguments to this attribute indicate the macro's role.
 For a macro that has multiple roles,
 apply the `attached` macro multiple times, once for each role.
 
-<!-- XXX TR:
-Is there a stable URL we can use to make the macro protocols below links?
-The current build of SwiftSyntax docs doesn't appear to include any of these protocols.
-That URL also looks like it includes a build number,
-so it seems likely to change over time.
-
-https://swiftpackageindex.com/apple/swift-syntax/508.0.0/documentation/swiftsyntax
+<!-- TODO:
+If there's a stable URL we can use, make the macro protocols below links.
 -->
 
 The first argument to this attribute
@@ -115,7 +110,7 @@ As a special case,
 you can write `prefixed($)`
 for a macro that behaves similar to a property wrapper.
 <!--
-XXX TR: Is there any more detail about this case?
+TODO TR: Is there any more detail about this case?
 -->
 
 ### available

TSPL.docc/ReferenceManual/Declarations.md

@@ -3479,7 +3479,7 @@ For more information, see <doc:Macros>.
 > *macro-definition* → **`=`** *expression*
 
 <!--
-XXX TR: Confirm that the 'where' clause goes after the equals sign.
+TODO TR: Confirm that the 'where' clause goes after the equals sign.
 -->
 
 ## Operator Declaration