Revert of Add more components_unittests to GN build

components/precache/core/BUILD.gn

Index: components/precache/core/BUILD.gn
diff --git a/components/precache/core/BUILD.gn b/components/precache/core/BUILD.gn
index 4aa14d0ee1f54d779088ebcd63cfeb41913de05c..ca972252b7973fc99d19c119a48e6ad7e39aff99 100644
--- a/components/precache/core/BUILD.gn
+++ b/components/precache/core/BUILD.gn
@@ -18,7 +18,7 @@
   ]
 }
 
-source_set("core") {
+static_library("core") {
   sources = [
     "precache_database.cc",
     "precache_database.h",
@@ -47,18 +47,3 @@
     "proto/precache.proto",
   ]
 }
-
-source_set("unit_tests") {
-  testonly = true
-  sources = [
-    "precache_database_unittest.cc",
-    "precache_fetcher_unittest.cc",
-    "precache_url_table_unittest.cc",
-  ]
-  deps = [
-    ":core",
-    ":proto",
-    "//testing/gmock",
-    "//testing/gtest",
-  ]
-}