printing: erase unused Printer member

We erased the effective_uri_ member of the Printer class in
https://crrev.com/c/1551683; this CL erases its declaration in the
header file.

Bug: chromium:838677
Test: CQ passes
Change-Id: I2a6307cf0a56b32ec30375aeaeeafc1f15fb3f28
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2382684Reviewed-by: Sean Kau <skau@chromium.org>
Commit-Queue: Kalvin Lee <kdlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803193}

chromeos/printing/printer_configuration.h

@@ -237,13 +237,6 @@ class CHROMEOS_EXPORT Printer {
   // Contains protocol, hostname, port, and queue.
   Uri uri_;
 
-  // When non-empty, the uri to use with cups instead of uri_.  This field
-  // is ephemeral, and not saved to sync service.  This allows us to do
-  // on the fly rewrites of uris to work around limitations in the OS such
-  // as CUPS not being able to directly resolve mDNS addresses, see crbug/626377
-  // for details.
-  std::string effective_uri_;
-
   // How to find the associated postscript printer description.
   PpdReference ppd_reference_;