Fix comments about filenames in some programs
diff --git a/programs/pkey/rsa_verify_pss.c b/programs/pkey/rsa_verify_pss.c
index 50d333b..ee92c82 100644
--- a/programs/pkey/rsa_verify_pss.c
+++ b/programs/pkey/rsa_verify_pss.c
@@ -100,7 +100,7 @@
     mbedtls_rsa_set_padding( mbedtls_pk_rsa( pk ), MBEDTLS_RSA_PKCS_V21, MBEDTLS_MD_SHA256 );
 
     /*
-     * Extract the RSA signature from the text file
+     * Extract the RSA signature from the file
      */
     ret = 1;
     mbedtls_snprintf( filename, 512, "%s.sig", argv[2] );