perf(module:select): remove unused types (#7850)

Author: xucr11

components/select/select-top-control.component.ts

@@ -138,7 +138,7 @@ export class NzSelectTopControlComponent implements OnChanges, OnInit, OnDestroy
   }
 
   tokenSeparate(inputValue: string, tokenSeparators: string[]): void {
-    const includesSeparators = (str: string | string[], separators: string[]): boolean => {
+    const includesSeparators = (str: string, separators: string[]): boolean => {
       // eslint-disable-next-line @typescript-eslint/prefer-for-of
       for (let i = 0; i < separators.length; ++i) {
         if (str.lastIndexOf(separators[i]) > 0) {
@@ -147,9 +147,9 @@ export class NzSelectTopControlComponent implements OnChanges, OnInit, OnDestroy
       }
       return false;
     };
-    const splitBySeparators = (str: string | string[], separators: string[]): string[] => {
+    const splitBySeparators = (str: string, separators: string[]): string[] => {
       const reg = new RegExp(`[${separators.join()}]`);
-      const array = (str as string).split(reg).filter(token => token);
+      const array = str.split(reg).filter(token => token);
       return [...new Set(array)];
     };
     if (