[webapp]fix error: Invalid version: "15.2-15.3"

web-app/.browserslistrc

@@ -11,7 +11,7 @@
 last 1 Chrome version
 last 1 Firefox version
 last 2 Edge major versions
-last 2 Safari major versions
+# last 2 Safari major versions
 last 2 iOS major versions
 Firefox ESR
 not IE 11 # Angular supports IE 11 only as an opt-in. To opt-in, remove the 'not' prefix on this line.