test: rename SideEffect -> SideEffects in Concat, Delay, and Item tests

50+ test files already use the plural 'SideEffects' module name.
Concat.Tests.fs, Delay.Tests.fs, and Item.Tests.fs were the only
outliers still using the singular form 'SideEffect'.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]

release-notes.txt

@@ -2,6 +2,7 @@
 Release notes:
 
 Unreleased
+    - test: rename `SideEffect` module to `SideEffects` in TaskSeq.Concat.Tests.fs, TaskSeq.Delay.Tests.fs, and TaskSeq.Item.Tests.fs for consistency with the rest of the test suite (50+ files already use the plural form)
     - test: add SideEffects module and ImmTaskSeq variant tests to TaskSeq.ChunkBy.Tests.fs, improving coverage for chunkBy and chunkByAsync
     - fixes: `Async.bind` signature corrected from `(Async<'T> -> Async<'U>)` to `('T -> Async<'U>)` to match standard monadic bind semantics (same as `Task.bind`); the previous signature made the function effectively equivalent to direct application
     - refactor: simplify splitAt 'rest' taskSeq to use while!, removing redundant go2 mutable and manual MoveNextAsync pre-advance

src/FSharp.Control.TaskSeq.Test/TaskSeq.Concat.Tests.fs

@@ -181,7 +181,7 @@ module Immutable =
             |> consumeTaskSeq
         |> should throwAsyncExact typeof<NullReferenceException>
 
-module SideEffect =
+module SideEffects =
     [<Fact>]
     let ``TaskSeq-concat executes side effects of nested (taskseq)`` () =
         let mutable i = 0

src/FSharp.Control.TaskSeq.Test/TaskSeq.Delay.Tests.fs

@@ -30,7 +30,7 @@ module Immutable =
         |> TaskSeq.delay
         |> validateSequence
 
-module SideEffect =
+module SideEffects =
     [<Fact>]
     let ``TaskSeq-delay executes side effects`` () = task {
         let mutable i = 0

src/FSharp.Control.TaskSeq.Test/TaskSeq.Item.Tests.fs

@@ -105,7 +105,7 @@ module Immutable =
         tail |> should equal (Some 10)
     }
 
-module SideEffect =
+module SideEffects =
     [<Theory; ClassData(typeof<TestSideEffectTaskSeq>)>]
     let ``TaskSeq-item prove it searches the whole sequence`` variant = task {
         let ts = Gen.getSeqWithSideEffect variant