Fixed misspelled references to browser_switcher headers

Some isolate step errors in trybots mentioned these non-existing
headers so hoping the trybots will be happier, this patch removes
and changes the names to point to existing files.

Bug: 881589
Change-Id: I6c7728110a9ce162293c57606824140cdacd8d38
Reviewed-on: https://chromium-review.googlesource.com/c/1286660Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#601133}

chrome/browser/BUILD.gn

@@ -3439,10 +3439,9 @@ jumbo_split_static_library("browser") {
 
   if (is_win || (is_linux && !is_chromeos)) {
     sources += [
+      "browser_switcher/alternative_browser_driver.h",
       "browser_switcher/alternative_browser_driver_linux.cc",
-      "browser_switcher/alternative_browser_driver_linux.h",
       "browser_switcher/alternative_browser_driver_win.cc",
-      "browser_switcher/alternative_browser_driver_win.h",
       "browser_switcher/alternative_browser_launcher.cc",
       "browser_switcher/alternative_browser_launcher.h",
       "browser_switcher/browser_switcher_navigation_throttle.cc",