Update bootstrap documentation to require JDK 11, not JDK 8

PiperOrigin-RevId: 422624281
diff --git a/site/docs/install-compile-source.md b/site/docs/install-compile-source.md
index 6b834da..9588364 100644
--- a/site/docs/install-compile-source.md
+++ b/site/docs/install-compile-source.md
@@ -194,7 +194,7 @@
 
 *   **C++ build toolchain**
 
-*   **JDK.** Versions 8 and 11 are supported.
+*   **JDK.** Version 11 is required.
 
 *   **Python**. Versions 2 and 3 are supported, installing one of them is
     enough.