Undo regex type rename

Unnecessary breaking change for now

src/eval/str.rs

@@ -567,7 +567,7 @@ impl Hash for Regex {
 }
 
 cast! {
-    type Regex: "regex",
+    type Regex: "regular expression",
 }
 
 /// A pattern which can be searched for in a string.

src/model/selector.rs

@@ -241,7 +241,7 @@ impl Reflect for ShowableSelector {
             CastInfo::Type("function"),
             CastInfo::Type("label"),
             CastInfo::Type("string"),
-            CastInfo::Type("regex"),
+            CastInfo::Type("regular expression"),
             CastInfo::Type("symbol"),
             CastInfo::Type("selector"),
         ])
@@ -250,7 +250,12 @@ impl Reflect for ShowableSelector {
     fn castable(value: &Value) -> bool {
         matches!(
             value.type_name(),
-            "symbol" | "string" | "label" | "function" | "regex" | "selector"
+            "symbol"
+                | "string"
+                | "label"
+                | "function"
+                | "regular expression"
+                | "selector"
         )
     }
 }

tests/typ/compiler/show-node.typ

@@ -96,7 +96,7 @@ Hey
 = Heading
 
 ---
-// Error: 7-10 expected function, label, string, regex, symbol, or selector, found color
+// Error: 7-10 expected function, label, string, regular expression, symbol, or selector, found color
 #show red: []
 
 ---