Use double quotes consistently in en-US (#24141)

Also removes quotes in commit messages related to file modifications
made in the Web UI.

tests/integration/api_repo_file_create_test.go

@@ -214,7 +214,7 @@ func TestAPICreateFile(t *testing.T) {
 		req = NewRequestWithJSON(t, "POST", url, &createFileOptions)
 		resp = MakeRequest(t, req, http.StatusCreated)
 		DecodeJSON(t, resp, &fileResponse)
-		expectedMessage := "Add '" + treePath + "'\n"
+		expectedMessage := "Add " + treePath + "\n"
 		assert.EqualValues(t, expectedMessage, fileResponse.Commit.Message)
 
 		// Test trying to create a file that already exists, should fail