Fix some typos. (#406)

Sorry for a pedantic PR. I'm just tired of looking at messages
from an overly zealous spell checking tool every time I try
to pull an update into our source tree.

doc/spec.md

@@ -3197,7 +3197,7 @@ specified base, decimal by default.
 If `base` is zero, x is interpreted like an integer literal, the base
 being inferred from an optional base prefix such as `0b`, `0o`, or
 `0x` preceding the first digit.
-When the `base` is provided explictly, a matching base prefix is
+When the `base` is provided explicitly, a matching base prefix is
 also permitted, and has no effect.
 Irrespective of base, the string may start with an optional `+` or `-`
 sign indicating the sign of the result.

starlarkjson/json.go

@@ -12,5 +12,5 @@ import (
 	"go.starlark.net/lib/json"
 )
 
-// Module is an alias of json.Module for backwards import compatibilty
+// Module is an alias of json.Module for backwards import compatibility
 var Module = json.Module

syntax/scan_test.go

@@ -275,7 +275,7 @@ pass`, "pass newline pass EOF"}, // consecutive newlines are consolidated
 		if err != nil {
 			got = err.(Error).Error()
 		}
-		// Prefix match allows us to truncate errors in expecations.
+		// Prefix match allows us to truncate errors in expectations.
 		// Success cases all end in EOF.
 		if !strings.HasPrefix(got, test.want) {
 			t.Errorf("scan `%s` = [%s], want [%s]", test.input, got, test.want)