fix ls command in dash

The `colorize_version` command fails in dash (default /bin/sh on
Ubuntu) with an error like:

  local: v0.2.3: bad variable name

Instead of using a local variable, interpolate the function argument
directly to avoid the error.

nvm.sh

@@ -139,8 +139,7 @@ nvm_checksum() {
 }
 
 colorize_version() {
-  local VERSION=$1
-  echo -e "\033[0;34m$VERSION\033[0m"
+  echo -e "\033[0;34m$1\033[0m"
 }
 
 print_versions() {