fix(filtering): increase the min width of the filtering input

Author: MPopov

projects/igniteui-angular/src/lib/core/styles/components/grid/_grid-theme.scss

@@ -2376,7 +2376,7 @@
         igx-input-group {
             width: 100%;
             max-width: rem(200px);
-            min-width: rem(100px);
+            min-width: rem(140px);
         }
 
         igx-prefix:focus {