all: Fix comment typos

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GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4481

lib/osutil/atomic.go

@@ -21,7 +21,7 @@ var (
 
 // An AtomicWriter is an *os.File that writes to a temporary file in the same
 // directory as the final path. On successful Close the file is renamed to
-// it's final path. Any error on Write or during Close is accumulated and
+// its final path. Any error on Write or during Close is accumulated and
 // returned on Close, so a lazy user can ignore errors until Close.
 type AtomicWriter struct {
 	path string

lib/osutil/osutil.go

@@ -35,9 +35,9 @@ func TryRename(filesystem fs.Filesystem, from, to string) error {
 	})
 }
 
-// Rename moves a temporary file to it's final place.
+// Rename moves a temporary file to its final place.
 // Will make sure to delete the from file if the operation fails, so use only
-// for situations like committing a temp file to it's final location.
+// for situations like committing a temp file to its final location.
 // Tries hard to succeed on various systems by temporarily tweaking directory
 // permissions and removing the destination file when necessary.
 func Rename(filesystem fs.Filesystem, from, to string) error {
@@ -114,7 +114,7 @@ func withPreparedTarget(filesystem fs.Filesystem, from, to string, f func() erro
 
 // copyFileContents copies the contents of the file named src to the file named
 // by dst. The file will be created if it does not already exist. If the
-// destination file exists, all it's contents will be replaced by the contents
+// destination file exists, all its contents will be replaced by the contents
 // of the source file.
 func copyFileContents(filesystem fs.Filesystem, src, dst string) (err error) {
 	in, err := filesystem.Open(src)