Fix some links in docs/linux

The documents are already in linux/ so they should not have linux/ in the path,
otherwise the link will be invalid.

R=sky

Change-Id: Iff06ba371672bc5f1d7c06d54babb90e3b4edbcf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1992800
Auto-Submit: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#729782}

docs/linux/build_instructions.md

@@ -332,7 +332,7 @@ other settings):
 ### More links
 
 *   Information about [building with Clang](clang.md).
-*   You may want to [use a chroot](linux/using_a_chroot.md) to
+*   You may want to [use a chroot](using_a_chroot.md) to
     isolate yourself from versioning or packaging conflicts.
 *   Cross-compiling for ARM? See [LinuxChromiumArm](chromium_arm.md).
 *   Want to use Eclipse as your IDE? See

docs/linux/debugging.md

@@ -317,7 +317,7 @@ core-dump by sending SIGABRT to the relevant process:
 
 ## Breakpad minidump files
 
-See [minidump_to_core.md](linux/minidump_to_core.md)
+See [minidump_to_core.md](minidump_to_core.md)
 
 ## Running Tests
 

docs/linux/debugging_gtk.md

@@ -30,7 +30,7 @@ NOTE: I tried debugging pango in a similar manner, but for some reason gdb
 didn't pick up the symbols from the symbols from the `-dbg` package. I ended up
 building from source and setting my `LD_LIBRARY_PATH`.
 
-See [building_debug_gtk.md](linux/building_debug_gtk.md) for more on how
+See [building_debug_gtk.md](building_debug_gtk.md) for more on how
 to build your own debug version of GTK.
 
 ## Parasite