chore: update to lean 4.8.0-rc2 (#331)

This should fix some of the `lake exe cache` issues we have been seeing
before.

lake-manifest.json

@@ -4,7 +4,7 @@
  [{"url": "https://github.com/leanprover-community/batteries",
    "type": "git",
    "subDir": null,
-   "rev": "914ad4f90518b7a2373ad6742a9518903f207927",
+   "rev": "7b3c48b58fa0ae1c8f27889bdb086ea5e4b27b06",
    "name": "batteries",
    "manifestFile": "lake-manifest.json",
    "inputRev": "main",
@@ -22,7 +22,7 @@
   {"url": "https://github.com/leanprover-community/aesop",
    "type": "git",
    "subDir": null,
-   "rev": "f617e0673845925e612b62141ff54c4b7980dc63",
+   "rev": "e8c8a42642ceb5af33708b79ae8a3148b681c236",
    "name": "aesop",
    "manifestFile": "lake-manifest.json",
    "inputRev": "master",
@@ -58,7 +58,7 @@
   {"url": "https://github.com/leanprover-community/mathlib4",
    "type": "git",
    "subDir": null,
-   "rev": "544c1c46397244b93b6cdb6db9eb456969062b15",
+   "rev": "e749c891f437dae8cb594779a057281b42eaee7c",
    "name": "mathlib",
    "manifestFile": "lake-manifest.json",
    "inputRev": "master",
@@ -76,7 +76,7 @@
   {"url": "https://github.com/fgdorais/lean4-unicode-basic",
    "type": "git",
    "subDir": null,
-   "rev": "8b53cc65534bc2c6888c3d4c53a3439648213f74",
+   "rev": "effd8b8771cfd7ece69db99448168078e113c61f",
    "name": "UnicodeBasic",
    "manifestFile": "lake-manifest.json",
    "inputRev": "main",
@@ -94,7 +94,7 @@
   {"url": "https://github.com/leanprover/doc-gen4",
    "type": "git",
    "subDir": null,
-   "rev": "b91fea210b7b6b451f19c6344d1f82765b9607af",
+   "rev": "b334278bbe691cb41af3e472ea0a85b6be81e98e",
    "name": "«doc-gen4»",
    "manifestFile": "lake-manifest.json",
    "inputRev": "main",

lean-toolchain

@@ -1 +1 @@
-leanprover/lean4:v4.8.0-rc1
+leanprover/lean4:v4.8.0-rc2