Remove prepend-left-2 CSS rule

This removes the prepend-left-2 CSS rule
and replaces it for the gl-ml-` utility
class from GitLab-ui

app/assets/stylesheets/framework/common.scss

@@ -405,7 +405,6 @@ img.emoji {
 .prepend-top-16 { margin-top: 16px; }
 .prepend-top-20 { margin-top: 20px; }
 .prepend-top-32 { margin-top: 32px; }
-.prepend-left-2 { margin-left: 2px; }
 .prepend-left-4 { margin-left: 4px; }
 .prepend-left-5 { margin-left: 5px; }
 .prepend-left-8 { margin-left: 8px; }

ee/app/assets/javascripts/epic/components/sidebar_items/sidebar_date_picker.vue

@@ -242,7 +242,7 @@ export default {
           @newDateSelected="newDateSelected"
           @hidePicker="stopEditing"
         />
-        <span v-else class="d-flex value-content prepend-left-2">
+        <span v-else class="d-flex value-content gl-ml-1">
           <template v-if="dateFixed">
             <span>{{ dateFixedWords }}</span>
             <icon
@@ -283,7 +283,7 @@ export default {
           @click="toggleDateType(false)"
         />
         <span class="prepend-left-5">{{ __('Inherited:') }}</span>
-        <span class="value-content prepend-left-2">{{ dateFromMilestonesWords }}</span>
+        <span class="value-content gl-ml-1">{{ dateFromMilestonesWords }}</span>
         <icon
           v-if="isDateInvalid && !selectedDateIsFixed"
           v-popover="dateInvalidPopoverOptions"

ee/spec/frontend/epic/components/sidebar_items/__snapshots__/sidebar_date_picker_spec.js.snap

@@ -62,7 +62,7 @@ exports[`SidebarDatePicker renders expected template 1`] = `
       </span>
        
       <span
-        class="d-flex value-content prepend-left-2"
+        class="d-flex value-content gl-ml-1"
       >
         <span
           class="no-value"
@@ -91,7 +91,7 @@ exports[`SidebarDatePicker renders expected template 1`] = `
       </span>
        
       <span
-        class="value-content prepend-left-2"
+        class="value-content gl-ml-1"
       >
         None
       </span>