Make NodeJS and Java required to build (#9206)

docs/BuildFromSource.md

@@ -19,9 +19,8 @@ Building ASP.NET Core on Windows requires:
         PS> ./eng/scripts/InstallVisualStudio.ps1
         ```
 * Git. <https://git-scm.org>
-* (Optional) some optional components, like the SignalR Java client, may require
-    * NodeJS. LTS version of 10.14.2 or newer recommended <https://nodejs.org>
-    * Java Development Kit (JDK) v8 with Java Runtime Environment (JRE) v8. See https://www.oracle.com/technetwork/java/javase/downloads/index.html
+* NodeJS. LTS version of 10.14.2 or newer <https://nodejs.org>
+* Java Development Kit (JDK) v8 with Java Runtime Environment (JRE) v8. See https://www.oracle.com/technetwork/java/javase/downloads/index.html
 
 ### macOS/Linux
 
@@ -31,11 +30,10 @@ Building ASP.NET Core on macOS or Linux requires:
 * If using Linux, you need a machine with all .NET Core Linux prerequisites: <https://docs.microsoft.com/en-us/dotnet/core/linux-prerequisites>
 * At least 10 GB of disk space and a good internet connection (our build scripts download a lot of tools and dependencies)
 * Git <https://git-scm.org>
-* (Optional) some optional components, like the SignalR Java client, may require
-    * NodeJS. LTS version of 10.14.2 or newer recommended <https://nodejs.org>
-    * Java Development Kit 10 or newer. Either:
-        * OpenJDK <http://jdk.java.net/10/>
-        * Oracle's JDK <https://www.oracle.com/technetwork/java/javase/downloads/index.html>
+* NodeJS. LTS version of 10.14.2 or newer <https://nodejs.org>
+* Java Development Kit 10 or newer. Either:
+    * OpenJDK <http://jdk.java.net/10/>
+    * Oracle's JDK <https://www.oracle.com/technetwork/java/javase/downloads/index.html>
 
 ## Clone the source code