Add template keyword to example comment for Layout::WithStaticSizes.

Without this keyword, we can sometimes get cryptic compilation failures such as "error: expected ';' after alias declaration".

PiperOrigin-RevId: 616933517
Change-Id: I2209f3899a4ac03c031217cec67de25bd376d355

absl/container/internal/layout.h

diff --git a/absl/container/internal/layout.h b/absl/container/internal/layout.h
index 72c1411..d42651a 100644
--- a/absl/container/internal/layout.h
+++ b/absl/container/internal/layout.h
@@ -85,9 +85,9 @@
 // generate optimal code. To help the compiler do that in more cases, you can
 // specify the fixed sizes using `WithStaticSizes`. This ensures that all
 // computations that can be performed at compile time are indeed performed at
-// compile time. E.g.:
+// compile time. Note that sometimes the `template` keyword is needed. E.g.:
 //
-//   using SL = L::WithStaticSizes<1, 1>;
+//   using SL = L::template WithStaticSizes<1, 1>;
 //
 //   void Use(unsigned char* p) {
 //     // First, extract N and M.