docs: Correct spelling of 'declaration' in indexes documentation

Author: tabedzki

docs/src/design/tables/indexes.md

@@ -35,7 +35,7 @@ To make searches faster on fields other than the primary key or a foreign key, y
 add a secondary index explicitly.
 
 Regular indexes are declared as `index(attr1, ..., attrN)` on a separate line anywhere in
-the table declration (below the primary key divide).
+the table declaration (below the primary key divide).
 
 Indexes can be declared with unique constraint as `unique index (attr1, ..., attrN)`.
 
@@ -62,7 +62,7 @@ Let’s now imagine that rats in a lab are identified by the combination of `lab
 @schema
 class Rat(dj.Manual):
     definition = """
-    lab_name : char(16) 
+    lab_name : char(16)
     rat_id : int unsigned # lab-specific ID
     ---
     date_of_birth = null : date
@@ -86,7 +86,7 @@ To speed up searches by the `rat_id` and `date_of_birth`, we can explicit indexe
 @schema
 class Rat2(dj.Manual):
     definition = """
-    lab_name : char(16) 
+    lab_name : char(16)
     rat_id : int unsigned # lab-specific ID
     ---
     date_of_birth = null : date