Bump idna from 3.8 to 3.15 in /llvm/utils/git

Bumps [idna](https://github.com/kjd/idna) from 3.8 to 3.15.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.md)
- [Commits](kjd/idna@v3.8...v3.15)

---
updated-dependencies:
- dependency-name: idna
  dependency-version: '3.15'
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

llvm/utils/git/requirements.txt

@@ -253,9 +253,9 @@ gitpython==3.1.50 \
     --hash=sha256:80da2d12504d52e1f998772dc5baf6e553f8d2fcfe1fcc226c9d9a2ee3372dcc \
     --hash=sha256:d352abe2908d07355014abdd21ddf798c2a961469239afec4962e9da884858f9
     # via -r requirements.txt.in
-idna==3.8 \
-    --hash=sha256:050b4e5baadcd44d760cedbd2b8e639f2ff89bbc7a5730fcc662954303377aac \
-    --hash=sha256:d838c2c0ed6fced7693d5e8ab8e734d5f8fda53a039c0164afb0b82e771e3603
+idna==3.15 \
+    --hash=sha256:048adeaf8c2d788c40fee287673ccaa74c24ffd8dcf09ffa555a2fbb59f10ac8 \
+    --hash=sha256:ca962446ea538f7092a95e057da437618e886f4d349216d2b1e294abfdb65fdc
     # via requests
 pycparser==2.22 \
     --hash=sha256:491c8be9c040f5390f5bf44a5b07752bd07f56edf992381b05c701439eec10f6 \

llvm/utils/git/requirements_formatting.txt

@@ -282,9 +282,9 @@ deprecated==1.2.14 \
     --hash=sha256:6fac8b097794a90302bdbb17b9b815e732d3c4720583ff1b198499d78470466c \
     --hash=sha256:e5323eb936458dccc2582dc6f9c322c852a775a27065ff2b0c4970b9d53d01b3
     # via pygithub
-idna==3.8 \
-    --hash=sha256:050b4e5baadcd44d760cedbd2b8e639f2ff89bbc7a5730fcc662954303377aac \
-    --hash=sha256:d838c2c0ed6fced7693d5e8ab8e734d5f8fda53a039c0164afb0b82e771e3603
+idna==3.15 \
+    --hash=sha256:048adeaf8c2d788c40fee287673ccaa74c24ffd8dcf09ffa555a2fbb59f10ac8 \
+    --hash=sha256:ca962446ea538f7092a95e057da437618e886f4d349216d2b1e294abfdb65fdc
     # via requests
 mypy-extensions==1.0.0 \
     --hash=sha256:4392f6c0eb8a5668a69e23d168ffa70f0be9ccfd32b5cc2d26a34ae5b844552d \