Remove note about AVX and LLVM 3.2 [ci skip]

I'm removing the note added in 6b0ccb4 regarding JuliaLang#3263, which seems
to be irrelevant now.  In particular, LLVM 3.2 is no longer supported,
so the note is misleading at best.  I think the best thing is to
remove it entirely, unless somebody objects.

README.md

@@ -222,7 +222,6 @@ These notes apply to the Debian 7 image currently available on Google Compute En
  Problem              | Possible Solution
 ------------------------|---------------------
  OpenBLAS build failure | Set one of the following build options in `Make.user` and build again: <ul><li> `OPENBLAS_TARGET_ARCH=BARCELONA` (AMD CPUs) or `OPENBLAS_TARGET_ARCH=NEHALEM` (Intel CPUs)<ul>Set `OPENBLAS_DYNAMIC_ARCH = 0` to disable compiling multiple architectures in a single binary.</ul></li><li> `OPENBLAS_NO_AVX2 = 1` disables AVX2 instructions, allowing OpenBLAS to compile with `OPENBLAS_DYNAMIC_ARCH = 1` using old versions of binutils </li><li> `USE_SYSTEM_BLAS=1` uses the system provided `libblas` <ul><li>Set `LIBBLAS=-lopenblas` and `LIBBLASNAME=libopenblas` to force the use of the system provided OpenBLAS when multiple BLAS versions are installed. </li></ul></li></ul><p> If you get an error that looks like ```../kernel/x86_64/dgemm_kernel_4x4_haswell.S:1709: Error: no such instruction: `vpermpd $ 0xb1,%ymm0,%ymm0'```, then you need to set `OPENBLAS_DYNAMIC_ARCH = 0` or `OPENBLAS_NO_AVX2 = 1`, or you need a newer version of `binutils` (2.18 or newer). ([Issue #7653](https://github.com/JuliaLang/julia/issues/7653))
-Illegal Instruction error | Check if your CPU supports AVX while your OS does not (e.g. through virtualization, as described in [this issue](https://github.com/JuliaLang/julia/issues/3263)), and try installing LLVM 3.3 instead of LLVM 3.2.
 
 ### OS X