tiff, tiff/lzw, vector: use single space in comments

Go style converged on using a single space after periods (see CL 20022).
Fix a couple places here that weren't consistent.

Change-Id: I856a34ee8a24bd033525baca55afd869158dd9ff
Reviewed-on: https://go-review.googlesource.com/c/image/+/469195
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

 tiff/lzw/reader.go | 4 ++--
 tiff/writer.go     | 2 +-
 vector/acc_test.go | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tiff/lzw/reader.go b/tiff/lzw/reader.go
index 1ccf585..0aae475 100644
--- a/tiff/lzw/reader.go
+++ b/tiff/lzw/reader.go
@@ -18,11 +18,11 @@ The tif_lzw.c file in the libtiff C library has this comment:
 
 ----
 The 5.0 spec describes a different algorithm than Aldus
-implements.  Specifically, Aldus does code length transitions
+implements. Specifically, Aldus does code length transitions
 one code earlier than should be done (for real LZW).
 Earlier versions of this library implemented the correct
 LZW algorithm, but emitted codes in a bit order opposite
-to the TIFF spec.  Thus, to maintain compatibility w/ Aldus
+to the TIFF spec. Thus, to maintain compatibility w/ Aldus
 we interpret MSB-LSB ordered codes to be images written w/
 old versions of this library, but otherwise adhere to the
 Aldus "off by one" algorithm.
diff --git a/tiff/writer.go b/tiff/writer.go
index 4272c5a..5d46184 100644
--- a/tiff/writer.go
+++ b/tiff/writer.go
@@ -280,7 +280,7 @@ type Options struct {
 	Compression CompressionType
 	// Predictor determines whether a differencing predictor is used;
 	// if true, instead of each pixel's color, the color difference to the
-	// preceding one is saved.  This improves the compression for certain
+	// preceding one is saved. This improves the compression for certain
 	// types of images and compressors. For example, it works well for
 	// photos with Deflate compression.
 	Predictor bool
diff --git a/vector/acc_test.go b/vector/acc_test.go
index 439c489..3579b0d 100644
--- a/vector/acc_test.go
+++ b/vector/acc_test.go
@@ -292,7 +292,7 @@ var sixteen float32 = 16
 //	0.0142602495543672
 //	0.014260249212384224
 //
-// On GOARCH=wasm,  printing x and y gives:
+// On GOARCH=wasm, printing x and y gives:
 //
 //	0.0142602495543672
 //	0.0142602495543672