15 RFR (XXS) 8250216: The README need not mention retrieving source code

[mark.reinhold at oracle.com]

Bug: https://bugs.openjdk.java.net/browse/JDK-8250216

The README at the root of the source tree says, “For information about
building the JDK, including how to retrieve all of the source code,
please see ...” yet we haven’t needed instructions on how to retrieve
the rest of the source code since JDK 10, when we consolidated
everything into a single repository.

(Also, the http://openjdk.java.net/ URL should be https://...)

Patch below.

Thanks,
- Mark

----

diff --git a/README b/README
--- a/README
+++ b/README
@@ -2,11 +2,10 @@
 Welcome to the JDK!
 ===================
 
-For information about building the JDK, including how to retrieve all
-of the source code, please see either of these files:
+For build instructions, please see either of these files:
 
   * doc/building.html   (html version)
   * doc/building.md     (markdown version)
 
-See http://openjdk.java.net/ for more information about the OpenJDK
+See https://openjdk.java.net/ for more information about the OpenJDK
 Community and the JDK.