test: fix two typos in float_lit2.go

Noted by gri in CL 100660044 review but I missed them.

TBR=gri
CC=golang-codereviews
https://golang.org/cl/97570049

test/float_lit2.go

@@ -16,9 +16,9 @@ import (
 // The largest exact float32 is f₁ = (1+(1-2²³))×2¹²⁷ = (1-2²⁴)×2¹²⁸ = 2¹²⁸ - 2¹⁰⁴.
 // The next float32 would be f₂ = (1+1)×2¹²⁷ = 1×2¹²⁸, except that exponent is out of range.
 // Float32 conversion rounds to the nearest float32, rounding to even mantissa:
-// between f₁ and f₂, values closer to f₁ round to f₁and values closer to f₂ are rejected as out of range.
+// between f₁ and f₂, values closer to f₁ round to f₁ and values closer to f₂ are rejected as out of range.
 // f₁ is an odd mantissa, so the halfway point (f₁+f₂)/2 rounds to f₂ and is rejected.
-// The halfway point (f₁+f₂)/2 = 2¹²⁸ - 2¹⁰⁵.
+// The halfway point is (f₁+f₂)/2 = 2¹²⁸ - 2¹⁰⁵.
 //
 // The same is true of float64, with different constants: s/24/53/ and s/128/1024/.