Eliminates reference to Texas

Refs https://rt.perl.org/Ticket/Display.html?id=132179 and also #1520

writing-docs/STYLEGUIDE.md

@@ -84,14 +84,14 @@ stick to easily understandable names:
 If you want to add some fancy characters, please stick to
 [well-known characters from our Unicode set](https://docs.perl6.org/language/unicode_ascii).
 
-### Prefer non-Texas (non-ASCII) syntax in examples
+### Prefer non-ASCII syntax in examples
 
     my @infinite-sequence = 1,3...∞ # GOOD
     my @infinite-sequence = 1,3...Inf # OK, but rather not
     <a b c > ⊖ <c d e> # Good
     <a b c > (^) <c d e> # OK, but don't do that
 
-All operators have a ASCII (or Texas) equivalent, but they are more
+All operators have a ASCII equivalent, but they are more
 verbose and do not correspond exactly to the mathematical operator or constant
 they often represent. Please use that syntax whenever possible.