refactor: Remove method canCreateGrouperForLine()

It only created duplicate calls to methods which were
already been called by createGrouperFromLine(), so added new value.

And it was not even called in the tests.

Author: claremacrae

src/Query/Filter/Field.ts

@@ -275,30 +275,9 @@ export abstract class Field {
             return null;
         }
 
-        if (!this.canCreateGrouperForLine(line)) {
-            return null;
-        }
-
         return this.createGrouperFromLine(line);
     }
 
-    /**
-     * Returns true if the class can parse the given 'group by' instruction line.
-     *
-     * Current implementation simply checks whether the class does support grouping,
-     * and whether the line matches this.grouperRegExp().
-     * @param line - A line from a ```tasks``` block.
-     *
-     * @see {@link createGrouperFromLine}
-     */
-    public canCreateGrouperForLine(line: string): boolean {
-        if (!this.supportsGrouping()) {
-            return false;
-        }
-
-        return Field.lineMatchesFilter(this.grouperRegExp(), line);
-    }
-
     /**
      * Parse the line, and return either a {@link Grouper} object or null.
      *
@@ -309,8 +288,6 @@ export abstract class Field {
      * this method.
      *
      * @param line - A 'group by' line from a ```tasks``` block.
-     *
-     * @see {@link canCreateGrouperForLine}
      */
     public createGrouperFromLine(line: string): Grouper | null {
         if (!this.supportsGrouping()) {