Bug 1385085 - Drop unnecessary tooltool dependencies. r=darktrojan

The Rust toolchain comes from the Taskcluster build configuration now. It's
actually downloading both versions right now, unpacking this one then
deleting it and unpacking the one from Taskcluster.

mail/config/tooltool-manifests/win32/releng.manifest

@@ -5,14 +5,6 @@
     "algorithm": "sha512",
     "filename": "mozmake.exe"
   },
-  {
-    "version": "rustc 1.24.0 (123456789 2018-02-15) repack",
-    "size": 126242752,
-    "digest": "b25cfd1a6961f698f5cc9f1bdfce19c5657e921ca941789f64940a3516e41be1c5c083b109ee5ada1f023e8fd9c154615b2c4c27ef1b55d4a6527e905e07722b",
-    "algorithm": "sha512",
-    "filename": "rustc.tar.bz2",
-    "unpack": true
-  },
   {
     "version": "Visual Studio 2017 15.8.4 / SDK 10.0.17134.0",
     "digest": "ecf1e03f6f98f86775059a43f9e7dc7e326f6643d7c08962d9f614e4f5a65b1ca63fa1cfeb0f1a3c2474bf0d4318dda960b378beb2a44ecf8a91111207f4ece5",
@@ -30,13 +22,6 @@
     "digest": "196ac6a567c85559957dfe511c3d8654d23c94d5603259e19ccafe9d71e0e4ccee63ccc9a778f2699654b786cda54266108b7d4db543d01bb0b42545b4e6ec75",
     "size": 297118
   },
-  {
-    "size": 216733,
-    "digest": "7debd8ce46955eae345ebdf2ee6df3bfc3f3a547af1306f7fb099e38750f5ed9412af7155017574fc796f2bb8f37b5b7c4f91d838fa3dc422a776c230ba2d64b",
-    "algorithm": "sha512",
-    "filename": "xz.tar.bz2",
-    "unpack": true
-  },
   {
     "version": "Outlook 2010 Messaging API (repacked w/ updated MAPI.h)",
     "filename": "mapiheader-20190415.zip",

mail/config/tooltool-manifests/win64/releng.manifest

@@ -5,15 +5,6 @@
     "algorithm": "sha512",
     "filename": "mozmake.exe"
   },
-  {
-    "version": "rustc 1.24.0 (123456789 2018-02-15) repack",
-    "size": 216054063,
-    "digest": "34456ad3abffab49afdb70407793fe6a19b4be1380c9c0ee0547245566d71d42716effadf7cf90e1eade65856b2b17e6ddac534b9dfdc94f09131907e2672515",
-    "algorithm": "sha512",
-    "visibility": "public",
-    "filename": "rustc.tar.bz2",
-    "unpack": true
-  },
   {
     "version": "Visual Studio 2017 15.8.4 / SDK 10.0.17134.0",
     "digest": "ecf1e03f6f98f86775059a43f9e7dc7e326f6643d7c08962d9f614e4f5a65b1ca63fa1cfeb0f1a3c2474bf0d4318dda960b378beb2a44ecf8a91111207f4ece5",
@@ -31,14 +22,7 @@
     "digest": "196ac6a567c85559957dfe511c3d8654d23c94d5603259e19ccafe9d71e0e4ccee63ccc9a778f2699654b786cda54266108b7d4db543d01bb0b42545b4e6ec75",
     "size": 297118
   },
-  {
-    "size": 216733,
-    "digest": "7debd8ce46955eae345ebdf2ee6df3bfc3f3a547af1306f7fb099e38750f5ed9412af7155017574fc796f2bb8f37b5b7c4f91d838fa3dc422a776c230ba2d64b",
-    "algorithm": "sha512",
-    "filename": "xz.tar.bz2",
-    "unpack": true
-  },
-{
+ {
     "version": "Outlook 2010 Messaging API (repacked w/ updated MAPI.h)",
     "filename": "mapiheader-20190415.zip",
     "unpack": true,