upgrade handlebars 4.7.3 -> 4.7.6 to avoid optimist dep (#3517)

yarn.lock

@@ -1845,13 +1845,14 @@ graceful-fs@^4.1.11, graceful-fs@^4.1.15, graceful-fs@^4.1.2, graceful-fs@^4.1.6
   integrity sha512-a30VEBm4PEdx1dRB7MFK7BejejvCvBronbLjht+sHuGYj8PHs7M/5Z+rt5lw551vZ7yfTCj4Vuyy3mSJytDWRQ==
 
 handlebars@^4.0.3:
-  version "4.7.3"
-  resolved "https://registry.yarnpkg.com/handlebars/-/handlebars-4.7.3.tgz#8ece2797826886cf8082d1726ff21d2a022550ee"
-  integrity sha512-SRGwSYuNfx8DwHD/6InAPzD6RgeruWLT+B8e8a7gGs8FWgHzlExpTFMEq2IA6QpAfOClpKHy6+8IqTjeBCu6Kg==
+  version "4.7.6"
+  resolved "https://registry.yarnpkg.com/handlebars/-/handlebars-4.7.6.tgz#d4c05c1baf90e9945f77aa68a7a219aa4a7df74e"
+  integrity sha512-1f2BACcBfiwAfStCKZNrUCgqNZkGsAT7UM3kkYtXuLo0KnaVfjKOyf7PRzB6++aK9STyT1Pd2ZCPe3EGOXleXA==
   dependencies:
+    minimist "^1.2.5"
     neo-async "^2.6.0"
-    optimist "^0.6.1"
     source-map "^0.6.1"
+    wordwrap "^1.0.0"
   optionalDependencies:
     uglify-js "^3.1.4"
 
@@ -4565,6 +4566,11 @@ which@^1.2.1, which@^1.2.9, which@^1.3.0, which@^1.3.1:
   dependencies:
     isexe "^2.0.0"
 
+wordwrap@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/wordwrap/-/wordwrap-1.0.0.tgz#27584810891456a4171c8d0226441ade90cbcaeb"
+  integrity sha1-J1hIEIkUVqQXHI0CJkQa3pDLyus=
+
 wordwrap@~0.0.2:
   version "0.0.3"
   resolved "https://registry.yarnpkg.com/wordwrap/-/wordwrap-0.0.3.tgz#a3d5da6cd5c0bc0008d37234bbaf1bed63059107"