update doc to reference actual variable used in code

Author: jmrodri

README

@@ -210,7 +210,7 @@ for the SSH password, if required.
 Although there is a significant security risk, it is possible to set environment 
 variables for both of these passwords:
 
- * RHO_PASSPHRASE for the rho configuration file password
+ * RHO_PASSWORD for the rho configuration file password
 
  * RHO_AUTH_PASSWORD for the SSH password
 

doc/rho.1

@@ -468,8 +468,8 @@ IMPORTANT:
 Storing passwords in environment variables is especially dangerous. Be very cautious about using these environment variables in a production environment.
 .PP
 .TP
-.B RHO_PASSPHRASE
-The AES-128 encrypted $HOME/.rho.conf file must be accessed every time rho is run. This file stores all of the profile information. A passphrase must be entered to access this file; the phrase is set the first time the file is created. Normally, the command prompts for this passphrase and it must be entered manually. The RHO_PASSPHRASE environment variable sets the password.
+.B RHO_PASSWORD
+The AES-128 encrypted $HOME/.rho.conf file must be accessed every time rho is run. This file stores all of the profile information. A passphrase must be entered to access this file; the phrase is set the first time the file is created. Normally, the command prompts for this passphrase and it must be entered manually. The RHO_PASSWORD environment variable sets the password.
 .PP
 .TP
 .B  RHO_AUTH_PASSWORD