[components] Revert "Use the local server for testing"

This reverts commit 9f08e45.

In Glean v50 `testGetValue` methods are actually not gated on test
mode (it's still not recommended though and absolutely IS still a
test-only API for all intents and purposes).

Further it turns out that calling `GleanTestLocalServer` in one test
might influence the other test and we're seeing intermittens where
`BaselinePingTest` is trying to upload to `localhost:0`, which of course
is invalid.
I have not yet figured out how we can properly separate out the state.
Alternatively we could merge the 2 tests into a single one.

Fixes mozilla-mobile/android-components#11340

android-components/components/service/glean/src/main/java/mozilla/components/service/glean/testing/GleanTestLocalServer.kt

@@ -14,6 +14,10 @@ package mozilla.components.service.glean.testing
  * initialize Glean more than once but still want to send pings to a local
  * server for validation.
  *
+ * FIXME(bug 1787234): State of the local server can persist across multiple test classes,
+ * leading to hard-to-diagnose intermittent test failures.
+ * It might be necessary to limit use of `GleanTestLocalServer` to a single test class for now.
+ *
  * Example usage:
  *
  * ```

android-components/samples/glean/src/androidTest/java/org/mozilla/samples/glean/MainActivityTest.kt

@@ -4,14 +4,11 @@
 
 package org.mozilla.samples.glean
 
-import android.content.Context
-import androidx.test.core.app.ApplicationProvider
 import androidx.test.espresso.Espresso.onView
 import androidx.test.espresso.action.ViewActions.click
 import androidx.test.espresso.matcher.ViewMatchers.withId
 import androidx.test.ext.junit.rules.ActivityScenarioRule
 import androidx.test.ext.junit.runners.AndroidJUnit4
-import mozilla.components.service.glean.testing.GleanTestLocalServer
 import org.junit.Assert.assertEquals
 import org.junit.Assert.assertNotNull
 import org.junit.Rule
@@ -24,12 +21,6 @@ class MainActivityTest {
     @get:Rule
     val activityRule: ActivityScenarioRule<MainActivity> = ActivityScenarioRule(MainActivity::class.java)
 
-    @get:Rule
-    val gleanRule = GleanTestLocalServer(context, 0)
-
-    private val context: Context
-        get() = ApplicationProvider.getApplicationContext()
-
     @Test
     fun checkGleanClickData() {
         // We don't reset the storage in this test as the GleanTestRule does not