resources: remove outdated simple/README.md

Its information was moved into the toplevel README during review, but this
file was forgotten.

Change-Id: I9a876270f236d8b7131e6243ae79e382ea9240d6
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-resources/+/36675
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: Bobby R. Bruce <bbruce@ucdavis.edu>
diff --git a/src/simple/README.md b/src/simple/README.md
deleted file mode 100644
index c6b1ced..0000000
--- a/src/simple/README.md
+++ /dev/null
@@ -1,3 +0,0 @@
-Simple single input source userland/baremetal executables in C/C++ etc.
-
-How to build explained in `make help`.