docs(testing): fix typo in beforeEach Jasmine method name (#3275)

Author: AlexanderLukin

public/docs/ts/latest/guide/testing.jade

@@ -363,7 +363,7 @@ a#testbed
   The metadata lack `imports` because (a) the default testing module configuration already has what `BannerComponent` needs
   and (b) `BannerComponent` doesn't interact with any other components.
 
-  Call `configureTestingModule` within a `BeforeEach` so that,
+  Call `configureTestingModule` within a `beforeEach` so that,
   before each spec runs, the `TestBed` can reset itself to a base state.
   The base state includes a default testing module configuration consisting of the
   declarables (components, directives, and pipes) and providers (some of them mocked)
@@ -1843,7 +1843,7 @@ a#testbed-methods
 
   Internally, all static methods cover methods of the current runtime `TestBed` instance that is also returned by the `getTestBed()` function.
 
-  Call `TestBed` methods _within_ a `BeforeEach()` to ensure a fresh start before each individual test.
+  Call `TestBed` methods _within_ a `beforeEach()` to ensure a fresh start before each individual test.
 
   Here are the most important static methods, in order of likely utility.
 table