Replace "Return" with "Returns" in API documentations

The guidelines are explicit about how we shoulld start sentences with
"Returns" rather than "Return". So these instances should follow that way.

See also the enhancements at rails#50595.

activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb

@@ -475,7 +475,7 @@ def num_waiting_in_queue # :nodoc:
         @available.num_waiting
       end
 
-      # Return connection pool's usage statistic
+      # Returns the connection pool's usage statistic
       # Example:
       #
       #    ActiveRecord::Base.connection_pool.stat # => { size: 15, connections: 1, busy: 1, dead: 0, idle: 0, waiting: 0, checkout_timeout: 5 }

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -623,14 +623,14 @@ def advisory_locks_enabled? # :nodoc:
       # This is meant to be implemented by the adapters that support advisory
       # locks
       #
-      # Return true if we got the lock, otherwise false
+      # Returns true if we got the lock, otherwise false
       def get_advisory_lock(lock_id) # :nodoc:
       end
 
       # This is meant to be implemented by the adapters that support advisory
       # locks.
       #
-      # Return true if we released the lock, otherwise false
+      # Returns true if we released the lock, otherwise false
       def release_advisory_lock(lock_id) # :nodoc:
       end
 

activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb

@@ -133,7 +133,7 @@ def quote_default_expression(value, column) # :nodoc:
         def type_cast(value) # :nodoc:
           case value
           when Type::Binary::Data
-            # Return a bind param hash with format as binary.
+            # Returns a bind param hash with format as binary.
             # See https://deveiate.org/code/pg/PG/Connection.html#method-i-exec_prepared-doc
             # for more information
             { value: value.to_s, format: 1 }

activerecord/lib/active_record/connection_handling.rb

@@ -256,7 +256,7 @@ def connection
 
     attr_writer :connection_specification_name
 
-    # Return the connection specification name from the current class or its parent.
+    # Returns the connection specification name from the current class or its parent.
     def connection_specification_name
       if @connection_specification_name.nil?
         return self == Base ? Base.name : superclass.connection_specification_name

activerecord/lib/active_record/database_configurations/url_config.rb

@@ -45,7 +45,7 @@ def initialize(env_name, name, url, configuration_hash = {})
       end
 
       private
-        # Return a Hash that can be merged into the main config that represents
+        # Returns a Hash that can be merged into the main config that represents
         # the passed in url
         def build_url_hash
           if url.nil? || url.start_with?("jdbc:", "http:", "https:")

activerecord/lib/active_record/migration.rb

@@ -1512,7 +1512,7 @@ def ran?(migration)
         migrated.include?(migration.version.to_i)
       end
 
-      # Return true if a valid version is not provided.
+      # Returns true if a valid version is not provided.
       def invalid_target?
         @target_version && @target_version != 0 && !target
       end