cmd/compile/internal/ssa: match style and formatting

Format final sentence in paragraph and make sentence case to match style.

Change-Id: I991729257fea202509f59a928b943e10ef1761f4
GitHub-Last-Rev: 770bbf5
GitHub-Pull-Request: #75550
Reviewed-on: https://go-review.googlesource.com/c/go/+/705519
Reviewed-by: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>

Author: willfaught

src/cmd/compile/internal/ssa/README.md

@@ -48,8 +48,7 @@ However, certain types don't come from Go and are special; below we will cover
 
 Some operators contain an auxiliary field. The aux fields are usually printed as
 enclosed in `[]` or `{}`, and could be the constant op argument, argument type,
-etc.
-for example:
+etc. For example:
 
 	v13 (?) = Const64 <int> [1]