doc: remove cov and prof from /ref/cmd

Update #3400

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5921044

doc/reference-cmd.html

@@ -10,27 +10,25 @@ by the <a href="/cmd/go/">go</a> program.
 </p>
 
 <p>
-The most common way to run these programs is as a subcommand of the go
-program,
-for instance as "go fmt". Run like this, the command operates on complete
-packages of Go source code, with the go program invoking the underlying binary
-with arguments appropriate to package-level processing.
+The most common way to run these programs is as a subcommand of the go program,
+for instance as <code>go fmt</code>. Run like this, the command operates on
+complete packages of Go source code, with the go program invoking the
+underlying binary with arguments appropriate to package-level processing.
 </p>
 
 <p>
 The programs can also be run as stand-alone binaries, with unmodified arguments,
-using the go tool subcommand, such as "go tool vet".
-This style of invocation allows, for instance, checking a single source file rather than
-an entire package: "go tool vet myprogram.go" as compared to
-"go vet mypackage".
-Some of the commands, such as prof and yacc, are accessible
-only through the go tool subcommand.
+using the go <code>tool</code> subcommand, such as <code>go tool vet</code>.
+This style of invocation allows, for instance, checking a single source file
+rather than an entire package: <code>go tool vet myprogram.go</code> as
+compared to <code>go vet mypackage</code>.
+Some of the commands, such as <code>yacc</code>, are accessible only through
+the go <code>tool</code> subcommand.
 </p>
 
 <p>
-Finally, two of the commands, fmt and
-doc, are also installed as regular binaries called
-gofmt and godoc
+Finally, two of the commands, <code>fmt</code> and <code>doc</code>, are also
+installed as regular binaries called <code>gofmt</code> and <code>godoc</code>
 because they are so often referenced.
 </p>
 
@@ -63,12 +61,6 @@ details.
 <td>Cgo enables the creation of Go packages that call C code.</td>
 </tr>
 
-<tr>
-<td><a href="/cmd/cov/">cov</a></td>
-<td>&nbsp;&nbsp;&nbsp;&nbsp;</td>
-<td>Cov is a rudimentary code coverage tool.</td>
-</tr>
-
 <tr>
 <td><a href="/cmd/fix/">fix</a></td>
 <td>&nbsp;&nbsp;&nbsp;&nbsp;</td>
@@ -90,12 +82,6 @@ an independent <a href="/cmd/godoc/">godoc</a> command with more general options
 gofmt</a> command with more general options.</td>
 </tr>
 
-<tr>
-<td><a href="/cmd/prof/">prof</a></td>
-<td>&nbsp;&nbsp;&nbsp;&nbsp;</td>
-<td>Prof is a rudimentary real-time profiler.</td>
-</tr>
-
 <tr>
 <td><a href="/cmd/vet/">vet</a></td>
 <td>&nbsp;&nbsp;&nbsp;&nbsp;</td>