docs/lib: Fix smaller typos

The changes is lib/attrsets.nix make sure the names are consistent with
the names used in the respective description.

lib/attrsets.nix

@@ -127,7 +127,7 @@ rec {
 
     : A list of strings representing the attribute path to check from `set`
 
-    `e`
+    `set`
 
     : The nested attribute set to check
 
@@ -563,7 +563,7 @@ rec {
 
     : A list of attribute names to get out of `set`
 
-    `attrs`
+    `set`
 
     : The set to get the named attributes from
 

lib/generators.nix

@@ -131,7 +131,7 @@ rec {
   /**
     Generate a line of key `k` and value `v`, separated by
     character `sep`. If `sep` appears in `k`, it is escaped.
-    Helper for synaxes with different separators.
+    Helper for syntaxes with different separators.
 
     `mkValueString` specifies how values should be formatted.
 

lib/trivial.nix

@@ -1139,7 +1139,7 @@ in
     # Type
 
     ```
-    fromHexString :: String -> [ String ]
+    fromHexString :: String -> Int
     ```
 
     # Examples