html: fix typo in package doc

Change-Id: I3cacfadc0396c8ef85addd062d991bb6f5b0483a
Reviewed-on: https://go-review.googlesource.com/c/net/+/580035
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Commit-Queue: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Damien Neil <dneil@google.com>
Reviewed-by: Damien Neil <dneil@google.com>

Author: Juneezee

html/doc.go

@@ -104,7 +104,7 @@ tokenization, and tokenization and tree construction stages of the WHATWG HTML
 parsing specification respectively. While the tokenizer parses and normalizes
 individual HTML tokens, only the parser constructs the DOM tree from the
 tokenized HTML, as described in the tree construction stage of the
-specification, dynamically modifying or extending the docuemnt's DOM tree.
+specification, dynamically modifying or extending the document's DOM tree.
 
 If your use case requires semantically well-formed HTML documents, as defined by
 the WHATWG specification, the parser should be used rather than the tokenizer.