Bug 1749284 - Move nsFind tests into toolkit/components/find/test/mochitest. r=jfkthame

I follow the suggestion in [1] to put the mochitest under `test/mochitest/`.

[1] If you are adding a new test directory, make sure its name matches one of
the patterns in .eslintrc.js.
https://firefox-source-docs.mozilla.org/code-quality/lint/linters/eslint.html?highlight=eslintrc#i-have-valid-code-that-is-failing-the-no-undef-rule-or-can-t-be-parsed

Differential Revision: https://phabricator.services.mozilla.com/D136049

toolkit/components/find/moz.build

@@ -24,6 +24,8 @@ SOURCES += [
     "nsFindService.cpp",
 ]
 
+MOCHITEST_MANIFESTS += ["test/mochitest/mochitest.ini"]
+
 FINAL_LIBRARY = "xul"
 
 REQUIRES_UNIFIED_BUILD = True

toolkit/components/find/test/mochitest/mochitest.ini

@@ -0,0 +1,2 @@
+[test_bug499115.html]
+[test_nsFind.html]

toolkit/components/windowcreator/test/mochitest.ini

@@ -1,5 +1,3 @@
-[test_bug499115.html]
-[test_nsFind.html]
 [test_private_window_from_content.html]
 [test_window_open_position_constraint.html]
 skip-if = toolkit == 'android'