Revert "Add 'latest-fastcomp' sdk (#200)" (#202)

This reverts commit b4de632f3f.

This caused the ec2 mozilla builders to fail due to bundling lkgr.json. Reverting til we figure it out.

emsdk_manifest.json

@@ -199,15 +199,6 @@
     "activated_path": "%installation_dir%/emscripten",
     "activated_cfg": "LLVM_ROOT='%installation_dir%/bin';BINARYEN_ROOT='%installation_dir%'"
   },
-  {
-    "id": "waterfall",
-    "version": "fastcomp-%waterfall-lkgr%",
-    "bitness": 64,
-    "linux_url": "https://storage.googleapis.com/wasm-llvm/builds/linux/%waterfall-lkgr%/wasm-binaries.tbz2",
-    "install_path": "fastcomp/%waterfall-lkgr%",
-    "activated_path": "%installation_dir%/emscripten",
-    "activated_cfg": "LLVM_ROOT='%installation_dir%/fastcomp/bin';BINARYEN_ROOT='%installation_dir%'"
-  },
   {
     "id": "clang",
     "version": "e1.13.0",
@@ -1558,12 +1549,6 @@
     "uses": ["waterfall-upstream-%waterfall-lkgr%-64bit", "node-8.9.1-64bit"],
     "os": "linux"
   },
-  {
-    "version": "fastcomp-%waterfall-lkgr%",
-    "bitness": 64,
-    "uses": ["waterfall-fastcomp-%waterfall-lkgr%-64bit", "node-8.9.1-64bit"],
-    "os": "linux"
-  },
   {
     "version": "%precompiled_tag32%",
     "bitness": 32,