_content: remove repetitive words

Change-Id: I92daee0c86d00ae15a5859d158652feb1214f7f5
Reviewed-on: https://go-review.googlesource.com/c/website/+/611797
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Commit-Queue: Ian Lance Taylor <iant@google.com>

_content/blog/chacha8rand.md

@@ -237,7 +237,7 @@ In many ways it is an ideal statistical generator.
 Even so, PCG is not unpredictable.
 While the scrambling of bits to prepare the result does not
 expose the state directly like in the LCG and Go 1 generators,
-[PCG-XSL-RR can still be be reversed](https://pdfs.semanticscholar.org/4c5e/4a263d92787850edd011d38521966751a179.pdf),
+[PCG-XSL-RR can still be reversed](https://pdfs.semanticscholar.org/4c5e/4a263d92787850edd011d38521966751a179.pdf),
 and it would not be surprising if PCG-DXSM could too.
 For secrets, we need something different.
 

_content/blog/deadcode.md

@@ -28,7 +28,7 @@ A typical change might rewrite some existing function, taking care to
 ensure that its new behavior satisfies the needs of all existing callers.
 Sometimes, after putting in all that effort, we would discover to our
 frustration that one of the callers was never actually reached in any
-execution, so it could safely have been been deleted.
+execution, so it could safely have been deleted.
 If we had known this beforehand our refactoring task would have been
 easier.
 

_content/talks/2012/go-docs.slide

@@ -107,7 +107,7 @@ Docs:
 
 .code go-docs.slide /^\*.*previous/,/^\.code/
 
-* Revenge of the input for the the previous slide
+* Revenge of the input for the previous slide
 
 .code go-docs.slide /^\*.*redux/,/^\.code/
 

_content/talks/2014/gotham-context.slide

@@ -149,7 +149,7 @@ _After_the_last_value_has_been_received_from_a_closed_channel_c,_any_receive_fro
 
 Any number of goroutines can `select` on `<-ctx.Done()`.
 
-Examples and discussion in in [[/blog/pipelines][blog.golang.org/pipelines]].
+Examples and discussion in [[/blog/pipelines][blog.golang.org/pipelines]].
 
 Using `close` requires care.