_content/doc: emphasize need to remove existing installations

This change updates the Linux installation instructions to emphasize
the need to delete an existing Go tree in /usr/local/go before
untarring the downloaded archive.

This is a common mistake people seem to make on Linux, and it's known
to produce broken Go installations.

Updates golang/go#51760

Change-Id: Ia7375957a6034defc708add74cf3c2cf4dbee5d4
Reviewed-on: https://go-review.googlesource.com/c/website/+/393755
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Jamal Carvalho <jamalcarvalho@google.com>
Trust: Ian Lance Taylor <iant@google.com>
diff --git a/_content/doc/install.html b/_content/doc/install.html
index 06dfe85..e6758bc 100644
--- a/_content/doc/install.html
+++ b/_content/doc/install.html
@@ -81,20 +81,19 @@
-        Extract the archive you downloaded into /usr/local, creating a Go tree
-        in /usr/local/go.
-        <p>
-          <strong>Important:</strong> This step will remove a previous
-          installation at /usr/local/go, if any, prior to extracting.
-          Please back up any data before proceeding.
+        <strong>Remove any previous Go installation</strong> by deleting the /usr/local/go folder
+		(if it exists), then extract the archive you just downloaded into /usr/local, creating a fresh
+		Go tree in /usr/local/go:
+		<pre>
+$ rm -rf /usr/local/go && tar -C /usr/local -xzf <span id="linux-filename">go1.14.3.linux-amd64.tar.gz</span>
+		<p>
+          (You may need to run the command as root or through <code>sudo</code>).
-        <p>
-          For example, run the following as root or through <code>sudo</code>:
-        </p>
-        <pre>
-rm -rf /usr/local/go && tar -C /usr/local -xzf <span id="linux-filename">go1.14.3.linux-amd64.tar.gz</span>
-        >
+		<p>
+		  <strong>Do not</strong> untar the archive into an existing /usr/local/go tree. This is known to
+		  produce broken Go installations.
+		 </p>
         Add /usr/local/go/bin to the <code>PATH</code> environment variable.