Fix GLIcon size property

This MR removes the use-deprecated-sizes property in gl-icon component
in app/assets/javascripts/vue_shared/components/file_icon.vue and
updates the size prop to use the valid size 16 in the relevant files

Changelog: other

app/assets/javascripts/blob/components/blob_header_filepath.vue

@@ -29,7 +29,7 @@ export default {
     <slot name="filepath-prepend"></slot>
 
     <template v-if="blob.path">
-      <file-icon :file-name="blob.path" :size="18" aria-hidden="true" css-classes="mr-2" />
+      <file-icon :file-name="blob.path" :size="16" aria-hidden="true" css-classes="mr-2" />
       <strong
         class="file-title-name mr-1 js-blob-header-filepath"
         data-qa-selector="file_title_content"

app/assets/javascripts/diffs/components/diff_file_header.vue

@@ -306,7 +306,7 @@ export default {
       >
         <file-icon
           :file-name="filePath"
-          :size="18"
+          :size="16"
           aria-hidden="true"
           css-classes="gl-mr-2"
           :submodule="diffFile.submodule"

app/assets/javascripts/error_tracking/components/stacktrace_entry.vue

@@ -82,7 +82,7 @@ export default {
         <div v-if="hasCode" class="d-inline-block cursor-pointer" @click="toggle()">
           <gl-icon :name="collapseIcon" :size="16" class="gl-mr-2" />
         </div>
-        <file-icon :file-name="filePath" :size="18" aria-hidden="true" css-classes="gl-mr-2" />
+        <file-icon :file-name="filePath" :size="16" aria-hidden="true" css-classes="gl-mr-2" />
         <strong
           v-gl-tooltip
           :title="filePath"

app/assets/javascripts/merge_conflicts/merge_conflict_resolver_app.vue

@@ -120,7 +120,7 @@ export default {
           >
             <div class="js-file-title file-title file-title-flex-parent cursor-default">
               <div class="file-header-content" data-testid="file-name">
-                <file-icon :file-name="file.filePath" :size="18" css-classes="gl-mr-2" />
+                <file-icon :file-name="file.filePath" :size="16" css-classes="gl-mr-2" />
                 <strong class="file-title-name">{{ file.filePath }}</strong>
               </div>
               <div class="file-actions d-flex align-items-center gl-ml-auto gl-align-self-start">

app/assets/javascripts/vue_shared/components/file_icon.vue

@@ -95,7 +95,6 @@ export default {
       :name="folderIconName"
       :size="size"
       class="folder-icon"
-      use-deprecated-sizes
       data-qa-selector="folder_icon_content"
     />
   </span>

spec/frontend/blob/components/__snapshots__/blob_header_filepath_spec.js.snap

@@ -10,7 +10,7 @@ exports[`Blob Header Filepath rendering matches the snapshot 1`] = `
     cssclasses="mr-2"
     filemode=""
     filename="foo/bar/dummy.md"
-    size="18"
+    size="16"
   />
    
   <strong