doc: more doubled words

I wrote a tool.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/8695047

doc/gccgo_contribute.html

@@ -84,7 +84,7 @@ To run the gccgo test suite, run <code>make check-go</code> in your
 build directory.  This will run various tests
 under <code>gcc/testsuite/go.*</code> and will also run
 the <code>libgo</code> testsuite.  This copy of the tests from the
-main Go repository is run using the DejaGNU script found in
+main Go repository is run using the DejaGNU script found
 in <code>gcc/testsuite/go.test/go-test.exp</code>.
 </p>
 

doc/install.html

@@ -166,7 +166,7 @@ the <code>GOROOT</code> environment variable to your chosen path.
 </p>
 
 <p>
-Add the <code>bin</code> subdirectory of your Go root (for example, <code>c:\Go\bin</code>) to to your <code>PATH</code> environment variable.
+Add the <code>bin</code> subdirectory of your Go root (for example, <code>c:\Go\bin</code>) to your <code>PATH</code> environment variable.
 </p>
 
 <h4 id="windows_msi">MSI installer (experimental)</h4>