tools: Upgrade yarn-deduplicate to v3, the latest.

Might as well use the most up-to-date version of this tool. Looking
at the changelog [1], I don't see anything that should interfere
with our previous use of the tool. Version 2 dropped support for
Node < 10; we're recommending people to use Node 10. A small handful
of flags that we don't use (or don't document using, anyway) have
become variadic.

`tools/test deps` and `yarn yarn-deduplicate` still run fine at this
commit.

[1] https://github.com/atlassian/yarn-deduplicate/blob/master/CHANGELOG.md

package.json

@@ -141,6 +141,6 @@
     "redux-mock-store": "^1.5.1",
     "rollup": "^2.26.5",
     "typescript": "^3.9.7",
-    "yarn-deduplicate": "^1.1.1"
+    "yarn-deduplicate": "^3.0.0"
   }
 }

yarn.lock

@@ -3828,7 +3828,7 @@ command-exists@^1.2.8:
   resolved "https://registry.yarnpkg.com/command-exists/-/command-exists-1.2.9.tgz#c50725af3808c8ab0260fd60b01fbfa25b954f69"
   integrity sha512-LTQ/SGc+s0Xc0Fu5WaKnR0YiygZkm9eKFvyS+fRsU7/ZWFF8ykFM6Pc9aCVf1+xasOOZpO3BAVgVrKvsqKHV7w==
 
-commander@^2.10.0, commander@^2.19.0:
+commander@^2.19.0:
   version "2.20.3"
   resolved "https://registry.yarnpkg.com/commander/-/commander-2.20.3.tgz#fd485e84c03eb4881c20722ba48035e8531aeb33"
   integrity sha512-GpVkmM8vF2vQUkj2LvZmD35JxeJOLCwJ9cUkugyk2nuhbv3+mJvpLYYt+0+USMxE+oj+ey/lJEnhZw75x/OMcQ==
@@ -3838,6 +3838,11 @@ commander@^5.1.0:
   resolved "https://registry.yarnpkg.com/commander/-/commander-5.1.0.tgz#46abbd1652f8e059bddaef99bbdcb2ad9cf179ae"
   integrity sha512-P0CysNDQ7rtVw4QIQtm+MRxV66vKFSvlsQvGYXZWR3qFU0jlMKHZZZgw8e+8DSah4UDKMqnknRDQz+xuQXQ/Zg==
 
+commander@^6.1.0:
+  version "6.1.0"
+  resolved "https://registry.yarnpkg.com/commander/-/commander-6.1.0.tgz#f8d722b78103141006b66f4c7ba1e97315ba75bc"
+  integrity sha512-wl7PNrYWd2y5mp1OK/LhTlv8Ff4kQJQRXXAvF+uU/TPNiVJUxZLRYGj/B0y/lPGAVcSbJqH2Za/cvHmrPMC8mA==
+
 commander@~2.13.0:
   version "2.13.0"
   resolved "https://registry.yarnpkg.com/commander/-/commander-2.13.0.tgz#6964bca67685df7c1f1430c584f07d7597885b9c"
@@ -10632,7 +10637,7 @@ [email protected], scheduler@^0.17.0:
     loose-envify "^1.1.0"
     object-assign "^4.1.1"
 
-"semver@2 || 3 || 4 || 5", semver@^5.0.3, semver@^5.1.0, semver@^5.3.0, semver@^5.4.1, semver@^5.5.0, semver@^5.5.1, semver@^5.6.0:
+"semver@2 || 3 || 4 || 5", semver@^5.0.3, semver@^5.1.0, semver@^5.4.1, semver@^5.5.0, semver@^5.5.1, semver@^5.6.0:
   version "5.7.1"
   resolved "https://registry.yarnpkg.com/semver/-/semver-5.7.1.tgz#a954f931aeba508d307bbf069eff0c01c96116f7"
   integrity sha512-sauaDf/PZdVgrLTNYHRtpXa1iRiKcaebiKQ1BJdpQlWH2lCvexQdX55snPFyK7QzpudqbCI0qXFfOasHdyNDGQ==
@@ -12399,14 +12404,14 @@ yargs@^15.0.2, yargs@^15.1.0, yargs@^15.3.1:
     y18n "^4.0.0"
     yargs-parser "^18.1.2"
 
-yarn-deduplicate@^1.1.1:
-  version "1.1.1"
-  resolved "https://registry.yarnpkg.com/yarn-deduplicate/-/yarn-deduplicate-1.1.1.tgz#19b4a87654b66f55bf3a4bd6b153b4e4ab1b6e6d"
-  integrity sha512-2FDJ1dFmtvqhRmfja89ohYzpaheCYg7BFBSyaUq+kxK0y61C9oHv1XaQovCWGJtP2WU8PksQOgzMVV7oQOobzw==
+yarn-deduplicate@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/yarn-deduplicate/-/yarn-deduplicate-3.0.0.tgz#e5c219c48d687e3be79eff4c719d6d7ef372f094"
+  integrity sha512-Ps1JEurQJ7VHt4lFD1x7QLtnsfA0DxYzdz8jvu5q7mAw8JFgRC1Hqq46uC+NjSwf2wOlitTfbmWswMnnW2Gqfg==
   dependencies:
     "@yarnpkg/lockfile" "^1.1.0"
-    commander "^2.10.0"
-    semver "^5.3.0"
+    commander "^6.1.0"
+    semver "^7.3.2"
 
 zulip-markdown-parser@^1.0.6:
   version "1.0.6"