[Fix] remove nvm_supports_source_options

Fixes #2387

test/fast/Unit tests/nvm_supports_source_options

@@ -1,27 +0,0 @@
-#!/bin/sh
-
-die () { echo "$@" ; exit 1; }
-
-\. ../../../nvm.sh
-
-x=0
-i=0
-runs=5
-calls=500
-first_result=false
-if (nvm_supports_source_options && printf .); then
-  first_result=true
-fi
-while [ $x -le $runs ]; do
-  y=$x
-  x=$(( x + 1 ))
-  while [ $i -le $calls ]; do
-    this_result=false
-    if (nvm_supports_source_options && printf .); then
-      this_result=true
-    fi
-    [ $this_result = $first_result ] || die "call ${i}, run ${y} got ${this_result}; expected ${first_result}"
-    i=$(( i + 1 ))
-  done
-done
-echo "${runs} runs of ${calls} calls succeeded"