doc(Carousel): support dark theme (#2675)

* doc(Carousel): support dark theme

* refactor: 更新示例

src/BootstrapBlazor.Server/Components/Samples/Carousels.razor.css

@@ -3,7 +3,7 @@
 }
 
     .carousel-item-demo2 .demo-item {
-        background-color: #e9ecef;
+        background-color: rgba(var(--bs-body-color-rgb),.08);
         border-radius: var(--bs-border-radius);
         padding: 1rem 2rem;
     }

src/BootstrapBlazor/Components/Carousel/Carousel.razor.scss

@@ -7,7 +7,6 @@
     --bb-carousel-slide-border: #{$bb-carousel-slide-border};
     --bb-carousel-slide-bg: #{$bb-carousel-slide-bg};
     --bb-carousel-slide-color: #{$bb-carousel-slide-color};
-    --bb-carousel-target-bg: #{$bb-carousel-target-bg};
     overflow: hidden;
 
     [data-bs-slide] {
@@ -47,10 +46,6 @@
     .carousel-indicators {
         opacity: 1;
         transition: all .2s linear;
-
-        [data-bs-target] {
-            background-color: var(--bb-carousel-target-bg);
-        }
     }
 
     .carousel-inner, .carousel-item, .carousel-item img {

src/BootstrapBlazor/wwwroot/scss/theme/bootstrap.blazor.scss

@@ -155,7 +155,6 @@ $bb-carousel-slide-border-radisu: 50%;
 $bb-carousel-slide-border: solid 1px #e9ecef;
 $bb-carousel-slide-bg: rgba(31,45,61,.5);
 $bb-carousel-slide-color: #fff;
-$bb-carousel-target-bg: #606266;
 
 // CheckBox
 $bb-checkbox-label-padding-y: 6px;